Jamie,
Pretty hard to say with out more info. This is really a "I gotta be there" type
problem, but...
Do you get any error messages when they try to open the report/s?
I saw this once... user clicks the report button, and nothing happens at all. Others
users in the building ran fine. It was a XP/printer definition problem.
Check to see (via Windows Printers) what "Default" printer these users have designated.
Any commonality amongst the users experiencing the problem?
I had my client use a different printer as Default, the reports ran fine, and... when
they switched back to their normal default printer everything "auto-magically" started
working again.
Trying these things will help in your problem determination.