Ram is fine, restore the card to stock settings and see what happens. If that doesn't help make sure adobe flash is the most recent version as well as make sure your network card isn't being finicky. If that doesn't work then let us know and we will troubleshoot some more from there.
Also, if it is a problem with Youtube, it could be your download speed through your ISP. You can have the nicest system in the universe, but if your DL speed sucks, you are at its mercy.
Then use Rivatuner to bring it back to factory settings. Look up your cards factory settings via the manual or newegg. And i doubt you get a solid 20mb/s but I would also doubt that your connect hurts youtube so miserably that you notice.