The situation you describe may very well match that stated on Errata # 24 on the Specification Update document you referred to, and thus, as a recommendation, I'd suggest making sure the BIOS is updated, and if you've already done this, then, please, contact either your place of purchase or HP for board-wise troubleshooting and/or advice.
Yesterday, I updated BIOS to the last version, but the problem still there.
I also had try the workaround of Errordata #24 (set the PERFCTRLSTS register bit 3 and 2 set to 0), it doesn't help. Actually, they are already set to 0 by default.
Any information about changes from rev 13(B3) to rev 22(C2)? add snoop control feature? Thanks you very much!