I recently upgraded to Microsoft Office 2011 for Mac. Suddenly I couldn’t open most of my previously-saved files in Excel, and PPT wouldn’t let me save new files. I was receiving errors like this:
Turns out that my hard drive itself had problematic characters in its name; at some point I had inadvertently overridden its descriptive name and replaced it with ‘//’. Seeing that now, I would have assumed that those characters would be enough to make most any operating system burst into spontaneous dry heaves on the spot. But until the recent MS Office upgrade, both my Mac’s OS (Lion) and MS Office 2008 dealt with the quirky (albeit mistaken) drive name just fine.
Anyway, this is a known bug of MS Office 2011 that presumably will be fixed soon. In the meantime, if you’re receiving this bug, check your folder/directory and core hard drive names to be sure they don’t include any non-standard characters. I renamed my Mac’s hard drive and the issue was immediately resolved.