998Mhz? Are you telling me you're running 499Mhz HTT? I don't think even an AN8 Fatality or DFI has that sort of ceiling.. Did you get your numbers wrong? I'm guessing its just DDR499... in that case.. you're only running 248MHz HTT.. which is fairly modest for an A8V given you have a PC4000 (stop scaring ppl with overly huge numbers).
Like I said, rev 2 will have a working PCI/AGP lock and a revised BIOS.. I'm sure ASUS would somehow get the board working at higher HTT than 220MHz, but afaik, A8V rev 1 HTT overclocking abilities are bollocks..
Try pushing ur board at 9x280 or 8x290.. and see if you could pass SuperPi 1M or HEXUS Pifast without breaking AGP lock then post back.. 280Mhz HTT is considered a walk in the park for my AV8..