Index: src/ch/AsyncHttpFile.cpp
===================================================================
diff -u -N -r045540c818c374806d09742ef3d7a984d8d757d3 -rd0cfddc68b5ec4dc4e9b73b6f87aa97995c7cc54
--- src/ch/AsyncHttpFile.cpp	(.../AsyncHttpFile.cpp)	(revision 045540c818c374806d09742ef3d7a984d8d757d3)
+++ src/ch/AsyncHttpFile.cpp	(.../AsyncHttpFile.cpp)	(revision d0cfddc68b5ec4dc4e9b73b6f87aa97995c7cc54)
@@ -36,7 +36,7 @@
 	m_hFinishedEvent(NULL),
 	m_dwError(ERROR_SUCCESS)
 {
-	memset(&m_internetBuffers, 0, sizeof(INTERNET_BUFFERS));
+	memset(&m_internetBuffers, 0, sizeof(INTERNET_BUFFERSA));
 
 	m_tOpenRequest.pHttpFile = this;
 	m_tOpenRequest.eOperationType = CONTEXT_REQUEST::eInternetOpenUrl;
@@ -263,10 +263,6 @@
 	{
 		if(!::InternetCloseHandle(m_hOpenUrl))
 		{
-			DWORD dwError = GetLastError();
-			ATLTRACE(L"InternetCloseHandle failed with error: %lu\n", dwError);
-
-			SetErrorCode(dwError);
 			if(GetErrorCode() == ERROR_IO_PENDING)
 				return S_FALSE;
 			else
@@ -288,6 +284,14 @@
 		m_hFinishedEvent = nullptr;
 	}
 
+	memset(&m_internetBuffers, 0, sizeof(INTERNET_BUFFERSA));
+
+	m_tOpenRequest.pHttpFile = this;
+	m_tOpenRequest.eOperationType = CONTEXT_REQUEST::eInternetOpenUrl;
+
+	m_tReadRequest.pHttpFile = this;
+	m_tReadRequest.eOperationType = CONTEXT_REQUEST::eInternetReadFileEx;
+
 	return S_OK;
 }
 
Index: src/ch/UpdateChecker.cpp
===================================================================
diff -u -N -r045540c818c374806d09742ef3d7a984d8d757d3 -rd0cfddc68b5ec4dc4e9b73b6f87aa97995c7cc54
--- src/ch/UpdateChecker.cpp	(.../UpdateChecker.cpp)	(revision 045540c818c374806d09742ef3d7a984d8d757d3)
+++ src/ch/UpdateChecker.cpp	(.../UpdateChecker.cpp)	(revision d0cfddc68b5ec4dc4e9b73b6f87aa97995c7cc54)
@@ -93,11 +93,7 @@
 	m_hThread = CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)&CUpdateChecker::UpdateCheckThread, (void*)this, 0, NULL);
 	if(!m_hThread)
 	{
-		m_strLanguage.Empty();
-		m_strSite.Empty();
-		m_eResult = eResult_Undefined;
-		m_eUpdateChannel = UpdateVersionInfo::eStable;
-		m_bSendHeaders = true;
+		Cleanup();
 		return false;
 	}
 
@@ -120,9 +116,12 @@
 		m_hThread = NULL;
 	}
 
+	::ResetEvent(m_hKillEvent);
+
 	m_httpFile.Close();
 
 	::EnterCriticalSection(&m_cs);
+
 	m_strSite.Empty();
 	m_eUpdateChannel = UpdateVersionInfo::eStable;
 	m_strLanguage.Empty();
@@ -133,6 +132,8 @@
 	m_strDownloadAddress.Empty();
 	m_strReleaseNotes.Empty();
 	m_eResult = CUpdateChecker::eResult_Undefined;
+	m_bSendHeaders = true;
+
 	::LeaveCriticalSection(&m_cs);
 }
 
@@ -268,7 +269,7 @@
 		std::stringstream dataBuffer;
 
 		// open the connection and try to get to the file
-		std::wstring wstrUserAgent = pUpdateChecker->m_tUpdateHeaders.GetUserAgent();
+		std::wstring wstrUserAgent = pUpdateChecker->m_tUpdateHeaders.GetUserAgent((PCTSTR)pUpdateChecker->m_strLanguage, pUpdateChecker->m_eUpdateChannel);
 		std::wstring wstrHeaders;
 		if(pUpdateChecker->GetSendHeaders())
 			wstrHeaders = pUpdateChecker->m_tUpdateHeaders.GetHeaders((PCTSTR)pUpdateChecker->m_strLanguage, pUpdateChecker->m_eUpdateChannel);
Index: src/ch/UpdateHeaders.cpp
===================================================================
diff -u -N -r50007f112b77cba170e6c427fee5428bda2d9dc5 -rd0cfddc68b5ec4dc4e9b73b6f87aa97995c7cc54
--- src/ch/UpdateHeaders.cpp	(.../UpdateHeaders.cpp)	(revision 50007f112b77cba170e6c427fee5428bda2d9dc5)
+++ src/ch/UpdateHeaders.cpp	(.../UpdateHeaders.cpp)	(revision d0cfddc68b5ec4dc4e9b73b6f87aa97995c7cc54)
@@ -22,12 +22,13 @@
 #include <boost\lexical_cast.hpp>
 #include <string>
 #include "..\common\version.h"
+#include <boost/algorithm/string.hpp>
 
 UpdateHeaders::UpdateHeaders()
 {
 }
 
-std::wstring UpdateHeaders::GetUserAgent()
+std::wstring UpdateHeaders::GetUserAgent(const std::wstring& wstrLanguagePath, UpdateVersionInfo::EVersionType eUpdateChannel)
 {
 	std::wstring wstrUserAgent(PRODUCT_FULL_VERSION_T);
 	wstrUserAgent += L" (" +
@@ -36,20 +37,17 @@
 		boost::lexical_cast<std::wstring>(PRODUCT_VERSION3) + L"." +
 		boost::lexical_cast<std::wstring>(PRODUCT_VERSION4) + L")";
 
+	wstrUserAgent += L"; " + ParseLanguagePath(wstrLanguagePath);
 	wstrUserAgent += L"; " + m_tWindowsVersion.GetWindowsVersion();
 	wstrUserAgent += L"; " + m_tWindowsVersion.GetCpuArch();
+	wstrUserAgent += L"; " + GetUpdateChannel(eUpdateChannel);
 
 	return wstrUserAgent;
 }
 
 std::wstring UpdateHeaders::GetHeaders(const std::wstring& wstrLanguagePath, UpdateVersionInfo::EVersionType eUpdateChannel)
 {
-	std::wstring wstrLanguage;
-	size_t stPos = wstrLanguagePath.rfind(L'\\');
-	if(stPos != std::wstring::npos)
-		wstrLanguage = wstrLanguagePath.substr(stPos + 1);
-	else
-		wstrLanguage = L"unknown";
+	std::wstring wstrLanguage = ParseLanguagePath(wstrLanguagePath);
 
 	std::wstring wstrHeaders;
 
@@ -80,6 +78,20 @@
 	return wstrHeaders;
 }
 
+std::wstring UpdateHeaders::ParseLanguagePath(const std::wstring &wstrLanguagePath)
+{
+	std::wstring wstrLanguage;
+	size_t stPos = wstrLanguagePath.rfind(L'\\');
+	if(stPos != std::wstring::npos)
+		wstrLanguage = wstrLanguagePath.substr(stPos + 1);
+	else
+		wstrLanguage = L"unknown";
+
+	boost::ireplace_all(wstrLanguage, L".lng", L"");
+
+	return wstrLanguage;
+}
+
 std::wstring UpdateHeaders::GetUpdateChannel(UpdateVersionInfo::EVersionType eUpdateChannel)
 {
 	switch(eUpdateChannel)
Index: src/ch/UpdateHeaders.h
===================================================================
diff -u -N -r1f27a2022090cf7aaf827a3f1ad90d6fe0038518 -rd0cfddc68b5ec4dc4e9b73b6f87aa97995c7cc54
--- src/ch/UpdateHeaders.h	(.../UpdateHeaders.h)	(revision 1f27a2022090cf7aaf827a3f1ad90d6fe0038518)
+++ src/ch/UpdateHeaders.h	(.../UpdateHeaders.h)	(revision d0cfddc68b5ec4dc4e9b73b6f87aa97995c7cc54)
@@ -27,9 +27,11 @@
 public:
 	UpdateHeaders();
 
-	std::wstring GetUserAgent();
+	std::wstring GetUserAgent(const std::wstring& wstrLanguagePath, UpdateVersionInfo::EVersionType eUpdateChannel);
 	std::wstring GetHeaders(const std::wstring& wstrLanguagePath, UpdateVersionInfo::EVersionType eUpdateChannel);
 
+	std::wstring ParseLanguagePath(const std::wstring &wstrLanguagePath);
+
 private:
 	static std::wstring GetUpdateChannel(UpdateVersionInfo::EVersionType eUpdateChannel);
 
Index: src/ch/UpdaterDlg.cpp
===================================================================
diff -u -N -r045540c818c374806d09742ef3d7a984d8d757d3 -rd0cfddc68b5ec4dc4e9b73b6f87aa97995c7cc54
--- src/ch/UpdaterDlg.cpp	(.../UpdaterDlg.cpp)	(revision 045540c818c374806d09742ef3d7a984d8d757d3)
+++ src/ch/UpdaterDlg.cpp	(.../UpdaterDlg.cpp)	(revision d0cfddc68b5ec4dc4e9b73b6f87aa97995c7cc54)
@@ -318,11 +318,11 @@
 	if(iCurSel == CB_ERR)
 		return;
 
-	UpdateVersionInfo::EVersionType eFrequency = UpdateVersionInfo::eReleaseCandidate;
+	UpdateVersionInfo::EVersionType eVersionType = UpdateVersionInfo::eReleaseCandidate;
 	if(iCurSel < UpdateVersionInfo::EVersionType::eMax)
-		eFrequency = (UpdateVersionInfo::EVersionType)iCurSel;
+		eVersionType = (UpdateVersionInfo::EVersionType)iCurSel;
 
-	SetPropValue<PP_PUPDATECHANNEL>(GetConfig(), eFrequency);
+	SetPropValue<PP_PUPDATECHANNEL>(GetConfig(), eVersionType);
 	GetConfig().Write();
 
 	CheckForUpdates();
@@ -370,7 +370,8 @@
 		GetPropValue<PP_PLANGUAGE>(GetConfig()),
 		(UpdateVersionInfo::EVersionType)GetPropValue<PP_PUPDATECHANNEL>(GetConfig()),
 		m_bBackgroundMode,
-		!WindowsVersion::IsWindowsXP());
+		false	// disabled sending headers as it is causing issues with WinInet on WinXP and Win Vista
+	);
 }
 
 void CUpdaterDlg::EnableUpdateRelatedControls(bool bEnable)