Found using DSL Tools, but probably a more generic problem.
When regional options set to Turkish, the following vsct file
... more ...
results in a compile time error:
"File not found: Unable to locate 'stdidcmd.h' on the include paths provided"
The problem is, VS build process tries to resolve the additional include using the following path:
C:\PROGRAM FİLES\MİCROSOFT VİSUAL STUDİO 2008 SDK\VİSUALSTUDİOINTEGRATİON\COMMON\INC\stdidcmd.h
It appears that the uppercase conversion of the path does not use invariant culture. "i" is represented as "İ" in uppercase form in Turkish, not "I" as in English.
Microsoft.VsSDK.targets prepares the path in lowercase, so I'm guessing that the problem is somewhere around Microsoft.VisualStudio.CommandTable.VSCTCompiler in VSCT.exe . The issue is OS independent and can also be reproduced under Vista.