Please try the offline installer:
Firefox and other NPAPI browsers:
I'm still getting the same problem within Citrix XenApp when attempting to run some videos - for example the one on this page - BBC Sport - Sports Personality: What would you walk 500 miles for?.
When I go to the page, I get the following screen displayed even after using the offline installer:
Then when I use this link, I still get the grey box that I had before.
This is a Citrix dialog, not a Flash Player dialog. It looks like the "No, don't optimize content" option in that dialog is selectable, at which point you can probably dismiss it.
Citrix *is* licensed to distribute a version of Flash Player that they've optimized for use in virtualized environments; however, I'm not familiar enough with it to offer you support. You'll need to talk to them about it. I'm assuming that your network administrator needs to make it available or something.
You can find more about it here: