This problem is fixed for me in the latest firefox using the flashplugin-nonfree, so I guess it has been fixed.
firefox 3.0+nobinonly-0ubuntu0.8.04.1
flashplugin-nonfree 9.0.124.0ubuntu2 (no change since original report)
ubuntu 8.04 with kernel 2.6.24-19-generic amd64
This problem is fixed for me in the latest firefox using the flashplugin- nonfree, so I guess it has been fixed.
firefox 3.0+nobinonly- 0ubuntu0. 8.04.1
flashplugin-nonfree 9.0.124.0ubuntu2 (no change since original report)
ubuntu 8.04 with kernel 2.6.24-19-generic amd64