and a lot more links from http://www.google.com/search?q=acer+%22input+not+supported%22
It seems the videocard is giving a signal the monitor doesn't like.
It's not clear what "updated my videocard" means: updated the driver, replaced the fan, bought a new one?
Anaway, I'd start with changing the settings until you find something that works. If it doesn't work at all, it's time for a new videocard. Or a more accepting monitor.