KC,
Before you engage in a wholesale slaughter campaign, check out this thread.
http://forum.cakewalk.com/tm.aspx?m=2816240 There's a good chance the problem is system related, and may have something to do with your Radeon drivers/settings.
Also consider recent events or changes. Was it working fine on this system before? What has changed?
By way of example, I recently downloaded a minihost to check on a question another user had. It brought with it an ASIO driver, probably something similar to ASIO4All. Even though I wasn't using it, its mere presence on my machine was causing a conflict with my E-MU ASIO drivers.
Uninstalling Sonar should be a last resort, and in any case, uninstalling the VSTs should not be necessary.
Good luck.