Thanks for the response.

Those all sound right to me, but they all seem to apply to the server computer. What confuses me is that some computers are able to access the files just fine, even though they're set up the same way (AFAICT) as the computers that are acting up.

To further confuse things, the computer I'm writing this on, one of the problem PCs, WAS able to connect to the shares and view the files for about 5 minutes earlier. But then, just a few minutes later, could not. Ugh.