I couldn't find anything on the internet about what I am experiencing.

When I add an MFC ActiveX control project to my solution, I cannot work with 
the files in that project.
When a file from such project is open, the focus is continuously set to the 
text editor. So I cannot edit the string table resource, I cannot select a 
method in the drop-down menu on top of the code window, I cannot use 
autocomplete, I cannot type in the help index. For short, I cannot work with 
MFC projects.

When I open the files separatly, without opening the project, they do behave 
normal, but then I don't have autocomplete and cannot compile of course. Is 
this a known issue?

I'm using:

Microsoft Visual Studio .NET 2003 Service Pack 1 (KB918007)
Microsoft Visual C++ .NET   69586-335-0000007-18014