Did everything they said. No Adobe Download Manager in Add/Remove Programs. No getPlus files were found on search. Still, I used the uninstall tool, rebooted then attempted to reinstall Flash and got the same file corrupted message.
After that, I used the executable file recommended here: http://kb2.adobe.com/cps/191/tn_19166.html
I'm still having problems with some things like IMVU though I can watch videos on YouTube now. (I was able to watch them after I disabled AdBlockPlus for YouTube. I tried this at IMVU and nothing changed.)
I did notice something I'd never seen before. In Firefox, under Tools, I have "Error Console". Curious, I opened it and found a ton of errors and warnings like:
"Expected declaration but found '*'. Skipped to next declaration."
"Unknown property 'zoom'. Declaration dropped."
"extend failed, please check that all dependencies are included."
"YAHOO.widget.Panel is not a constructor"
"IMVU.AvatarCard.observeOnlineStatus is not a function"
"IMVU.badgeTooltip is undefined"
Does this stuff mean anything?