User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:2.0b10pre) Gecko/20110119 Firefox/4.0b10pre
Build Identifier: Mozilla/5.0 (Windows NT 6.1; rv:2.0b10pre) Gecko/20110119 Firefox/4.0b10pre
Open an app tab in a new window
Enter, exit and re-enter panorama using panorama button
Hit the right arrow button on keyboard
Result: A thin strip appears on the right of the window.
Mozilla/5.0 (X11; Linux i686; rv:7.0a1) Gecko/20110629 Firefox/7.0a1
Verified issue on Ubuntu 11.04, Mac OS X 10.6, WinXP and Win 7. I was unable to reproduce issue -> setting status to Verified Fixed.