here is some information to understand my situation better.
OS: windows 8.1
IDE: Visual Studio 2008 Pro
Language: C++
i have just my Firefox
It was because of an 32bit DLL, which should not be loaded for my 64bit Project.exe.
I have found this with Process Monitor.
I don't know why, but anyway is the "path" is changed and the 32bit DLL(which has the same name with 64bit DLL) is loaded..
If you have the same Problem, just start Process Monitor and check out dll files.