Unable to "save" or "save as" in Word 2007

I hope that someone out there can help me! I'm running Office Small Business 2007 on a Dell Optiplex 330 desktop with Windows XP. Office 2007 is also using Adobe Acrobat 9 as an add-on to create PDF files.  Everything was working just fine until the most recent Windows update just prior to this weekend.

Over the weekend I began noticing a problem. In Word, when creating a new document or saving an existing document with a new name, I am unable to save or "save as". When I attempt to save or save as, I hear an error sound, but nothing appears on the screen - no dialogue box, nothing.

The problem doesn't occur consistently. It happens more often than not, but not every time. If I reboot and then relaunch Word, I sometimes am able to save or save as.  I've tried launching Word in safe mode, but the problem occurs occasionally even in Safe Mode.

I've done everything I can think of to troubleshoot and address this issue. I've installed updates for Adobe Acrobat 9, I've got all the latest updates for Office 2007. I've run diagnostics, anti-virus and spyware programs, you name it, and nothing fixes it. I have been unable to find a fix for my problem, and I've desperately hunted everywhere on the web.

Might anyone out there be able to help me to find a fix for this annoying and persistent issue? Thanks kindly in advance!