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Felix,
I experience the same problems with empty menus as jimbobuk. I'll try to describe my setup and how I can reproduce it.
My mini with 10.5.1 (latest version of this update) and RB 1.8.1 (upgraded from 1.7 to 1.8 to 1.8.1) has Front Row as the default application when starting up. It also automatically connects to 2 network (samba) shares so 2 Finder Windows are open before Front Row gets active. No Bluetooth mouse is connected, only a Bluetooth keyboard.
After Front Row has (automatically) started, I exit it via the menu-button on the remote. I check the RB-menu by pressing the menu-button once and everything is fine. Then I exit the RB-menu.
Then I start Front Row by keeping the menu-button pressed. Front Row appears and I exit again via the menu-button. I check the RB-menu by pressing the menu-button once and I get an empty menu!
Hope this helps you reproduce this annoying problem. As I have no control on my Mac when this problem occurs, I need to reboot is via my other Mac using screen sharing. Or do you have another workaround?
Thanks,
John.