Thanks. I thought of that too, but permissions were fine in right-click properties.

I noticed that I also couldn't change any of the properties (Office Button -> Prepare -> Properties). Turns out the files he sent me have been saved as "shared" workbooks. Not too familiar with these yet. I'm also not sure if this was an intentional move by my boss, or (more likely) he inadvertently saved them as such without realizing what the implications were. The permissions weren't set properly to block any users from viewing or modifying the documents, so in effect the only thing he's done is disable several of the core features that would otherwise be available in Excel.

I don't think it was ever his intention to have multiple users working in the same document at the same time on the network (at least that's my interpretation of what the shared workbooks are). Now I gotta figure out how to undo the shared features.