DLLNotFoundException

Hi all, I am having this strange issue where I had a few projects running a DLL, and from one night to the next morning Unity started complaining about not being able to find the DLLs in any of my projects. That night I installed a few unrelated things (Dreamweaver, Cygwin) but other than that there was really no change. All these projects were running just fine before, and none of them are able to find the DLLs now (they are in the right location because it was they were being found before). I am wondering if anybody ran into an issue like this before, and if so how did you solve it? This is really holding me back from making any progress.

Thanks in advance