This could be similar to bug 6748069, which has a workaround that you could try on your HP machine:
Bug ID: 6748069 Synopsis: installation/boot hangs on Griffin with snv_87+ http://bugs.opensolaris.org/view_bug.do?bug_id=6748069 Or Bug ID: 6764872 Synopsis: resource conflict in pci MEM and Prefetch MEM http://bugs.opensolaris.org/view_bug.do?bug_id=6764872 ==> Disabling pci reprogramming by boot with: -B pci-reprog=off -- This message posted from opensolaris.org