I have 2 users attempting to access and check out documents from a
library. Until this week they had no problems. Now, when accessing
documents, they get the error message "The Document Workspace
associated with this document cannot be found. Contact your
administrator for more information." When they try to check out a doc,
they get the message "Value does not fall within the expected range."
No other users are having this problem (verified by 3 others) - and
they don't either if they access SharePoint from another person's PC.

I find no documentation on-line that links these 2 errors, but it
appears to be related to their machines - perhaps even their browsers.
Are there some specifics settings I should look for?

Further information just received: user is having the problem with IE8,
but not with Firefox. Again, is there a setting or parameter to look
for?