Blue Screen error message: APC Index Mismatch XPS 8900

I've been having the same problem since February, and despite several online sessions with Dell tech support, 4 Geek Squad sessions( I bought from Best Buy)  and 2 trips to the Dell repair center I am getting nowhere. This is 6 months old, still under warranty, yet all the repair center did was replace the hard drive, which did not resolve the issue. After talking with a Dell rep who barely understands English for two hours, the best he could offer was to do a hardware scan which of course, he has no record of even though it was done months ago.