I just installed 7.10 Ubuntu on my laptop and a desktop (both Dell) and everything works nice but when I load a page in FF that requires a flash plugin, I get the window pop up on the browser that indicates I am missing a plugin to view this page and there it shows me I need flash so I select the install flash option in the pop-up. It allows me to download flash and then restarts FF for me. The only problem is the plugin never works. I keep getting the missing plugin pop up but when I try to install a 2nd time, I get a message that says the plugin is already installed. I did not get a failure message when installing the plugin so I don't know why it is not working. I get this on both machines so I think this is related to 7.10.

Anyone know how to fix this?

don't if it's related or not, but the plugin firefox installs isn't necessarily the newest one...so if the site you try to access requires you have the last version it'll continue to complain about that.

one way to solve this could be to do a manual install : first, remove the plugin firefox has installed.
then, go to the adobe site, and get shockwave flash player (this will point to the latest version available) in the tar.gz format
untar it with then, close firefox and run the script flash-player-installer, answer the few questions and you're done.

when you apt-get install flashplugin-nonfree it is the latest one, it's downloaded from adobe. Which is the reason that it wasn't working for a while, adobe updated the flash plugin and the md5sum the installer checks was wrong. There is an updated package in the gutsy-proposed repository, however, so just enable that repository and update.