Comment 68 for bug 262693

Make sure you do NOT have multiple plugins installed.

dpkg -l | grep flash; dpkg -l | grep gnash; dpkg -l | grep swf

should NOT output other than:

flashplgin-nonfree

if it does, remove the other packages in some way (apt-get, aptitude, synaptic etc) and leave the 1 package in tact

You can also use:

http://download.macromedia.com/pub/labs/flashplayer10/libflashplayer-10.0.32.18.linux-x86_64.so.tar.gz

if you fancy using the 64bit flash (its alpha) just dro pthe file into your plugins folder and you are set, unfortunately this will not autoupdate with system updates.