We develop a WinForm application using Scintilla.NET (1.7) component, which uses SciLexer.dll (unamnaged). At run-time, we distribute both 32bit and 64bit SciLexer.dll, and we load the correct one when the application starts (everything works fine).

On our new development environments (Windows 7 64-bit), all our solutions build and run just fine, but the WinForm visual designer does not load our forms/controls which use Scintilla.NET, because it cannot load the correct SciLexer.dll:

Window class name is not valid. 

at System.Windows.Forms.NativeWindow.WindowClass.RegisterClass()
at System.Windows.Forms.NativeWindow.WindowClass.Create(String className, Int32 classStyle)
at System.Windows.Forms.NativeWindow.CreateHandle(CreateParams cp)
at System.Windows.Forms.Control.CreateHandle()
at System.Windows.Forms.Control.get_Handle()
at Scintilla.ScintillaControl.SendMessageDirect(UInt32 msg, IntPtr wParam, IntPtr lParam)
at Scintilla.ScintillaControl.SendMessageDirect(UInt32 msg)
at Scintilla.ScintillaControl.get_CodePage()
at Scintilla.ScintillaControl..ctor(String sciLexerDllName)
at Scintilla.ScintillaControl..ctor() 

Where does Visual Studio 2008 look for unmanaged libraries? I tried putting the 64-bit SciLexer.dll in SysWOW64, in the folder where ScintillaNET.dll is referenced, adding a folder in PATH system variable, adding a folder reference in the project, but I keep getting this error.

Any help is appreciated.