Hmm. DEP is supposed to prevent programs from trying to execute what's supposed to be data instead of code. Firefox shouldn't really be triggering that. Don't have time to read over the thread again but what plugins and add-ons are you running?
For add-ons, go to Tools -> Add-Ons for the list.
For plugins, go to the address bar and type aboutlugins and hit enter.
One of these might be causing the DEP error.
For add-ons, go to Tools -> Add-Ons for the list.
For plugins, go to the address bar and type aboutlugins and hit enter.
One of these might be causing the DEP error.