setting a breakpoint at the entrance to function RADEONEnterVT() shows me that it gets there and when i continue after that it locks, indicating that the problem is after the entrance.  After adding breakpoints at the following lines I saw the corresponding behavior:

9102: did not reach before a crash  (this is right after RADEONWaitForIdleMMIO(pScrn);)

9093: reached without a crash (right after pInt = xf86InitInt10 (info->pEnt->index);)  upon "next'ing" to advance through the problem area I find that execution of line 9095 (xf86ExecX86int10 (pInt);) (so i was at this line and just hit next) causes it to hard-lock.