> We can repeatedly get pax to hang like this during an install using boot 
> floppies from a release built from feb 9 sources or from todays source.

Having just remembered that the install kernel has ddb built in we had a 
little poke.  trace gives the (not very informative) output

(null)(c082bd60,cb002eb8,c02b127e,1,cb002ec8) at 0xc024cce0
(null)(1) at 0xc02b12c7
(null) ...
(null) ...
(null) ...
Bad frame pointer: 0xc0839780

and ps shows pax is waiting on "uvn_fp2" and as you would expect there are few 
other processes running (sysinst and some kernel processes)

We have a machine in this state at the moment if there is something we can 
usefully do with it to help track this down.

cheers
mark