Comment 34 for bug 600158

Ok, fixed.
I re-run the suggested script to remove old versions of flash AND then "Disabled" the flash version 9.xx indicated in the add-ons/plugins.
Running the script alone was not enough. about:plugins still was indicating the flash 9.x version present, even if the 10.x version was present.

So to fix my firefox I had to :
- close firefox
- run the script posted by Peter
- start firefox (about:plugins was still indicating the presence of 9.xx flash plugin)
- disable the flash plugin from Tools/Add-on/plugins
- close firefox
- start firefox (abou:plugins now is indicating NO flash plugin present)
- install flash plugin

it works now.