Report Generates Blank Page

[CognosMyCognos]

I'm having an issue with a couple of users where when they run a report via Cognos Connection the pdf renders blank.  However, if they hit the back button and run the report a second time it renders just fine.

It's only happening with a couple of users so it's not environment related.  They're both running Acrobat 9 Pro, IE8 and Windows 7 (as are other users NOT having this issue).  Neither user has any Google, Yahoo, etc toolbars running.

I had a third user encounter this issue a few months ago and she swears I did something to fix it, but I can't remember if I really did anything.  I really think it just stopped happening on its own.

Has anyone encountered anything like this?  If so, what did you do to fix it?

thanks