Run-time Error 5

Every time I open an existing or new document in Microsoft Word, a box pops up with Run-time error '5' and I must click 'End' in order to access the document. This began happening just today, without any apparent cause. Microsoft Word had frozen previously, but I had a lot of documents open so I wasn't surprised. The problem began the next time I opened the program. 

I've tried uninstalling and reinstalling Office to no avail. Not knowing what the problem is I'm hesitant to continue editing my documents, in case they become corrupted. 

Any suggestions much appreciated.