We have been seeing some strange issues with new windows, sessions, etc. with IE8 over the last few weeks (particularly). Do not have any definitive answers yet but may have something to do with the IE security fixes that came out recently. If you (or your users -- not sure what role you have) have the ability to log a service request I would suggest doing so to allow us to better troubleshoot and track these issues.
I will come back and update this thread when we have something more definitive. Right now we are trying to catalog the various behaviors we are seeing and determine what might be going on.
Stevan - Oracle