Can't dump stacks from modern GDB on Linux

I just found that I can no longer dump VW stacks from GDB. I used to be
able to. Now, I get this kind of thing for any dumping function:


   (gdb) p dumpAllProcessesToFile(1,1,1)
   Warning:
   Cannot insert breakpoint -79.
   Error accessing memory address 0xf7f7347b: Input/output error.

I've tried this with both VW7.5 and with a 7.4d engine on 7.4.1, with
the same result.

It could be the version of GDB, I recently built a new machine. My GDB
version is 6.6.

Anyone else seen this, or know of a solution?

Thanks,

-Martin