Just as an update I upgraded to latest NVidia drivers and flash has become much less stable. Strace of the npviewer system showed a lots of time outs with resource unavailable - just checked my dmesg and found this:
npviewer.bin[10573]: segfault at 418 ip 00000000f60c4d36 sp 00000000ffeb8748 error 6 in libflashplayer.so[f5e57000+b5f000] -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/764620 Title: Flash video's showing up when minimized in on other application's black areas -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs