[Hampshire] Skype fails and takes out Gutsy

Hi,

Having converted SWMBO's PC to Ubuntu I am now embarrassed that one
much used app, skype, is misbehaving big time. After a minute or so
of use (with a USB headset), Skype just stops working. After a
further short delay it then disappears from the GUI. The strange
thing is that it leaves an apparently working system but with some
very odd behaviour:

1) You can't restart Skype, it says there is another instance running.
2) killall -9 skype can be issued as often as you like with no error
message
3) ps ax fails to complete, hanging whichever terminal runs the
command. Even killall -9 ps from another terminal doesn't get the ps
terminal back.
4) pgrep and pkill also hang

The only way back I've found is to shut down the PC (but normal
shutdown doesn't work, presumably because of the unkillable skype) so
you end up just switching off - nasty! I've tried 3 different
versions of Skype so I think it's quite likely to be a USB sound
problem rather than a problem specifically with Skype.

It's hard to investigate when the basic tools stop working! Can anyone
think what might be happening? Is there any way of getting ps
information direct from /sys or /proc or other magic to help find out
what's going on?

TIA, Peter