assembly missing issue

Hi NG,

I'm fighting an issue with my assemblies (who does not :-) ).

I got a couple of libraries which I use in different projects (that's what
they are for, aren't they?) and which partially depend on each other (in a
hierarchy - no circles).
In my current project I have a base form which is called "frmBase" from
which all of my other forms inherit. All of this forms use functionalities
from my libraries.
This morning I opened the main form in the designer and got an error message
like this:
"Error while instantiating frmBase: File or assembly name 'xyz' or a
dependency was not found." (The original message is in german...)
But when I open the mentioned form frmBase, this error does not occur.
The mentioned assembly is available and readable...

What worries me most is the fact, that last week everything was working
fine. I'm not sure what might have changed in my setup recently that leads
to this issue.

Any help highly appreciated!

Thanks,
Thorsten