yum, rpm, pirut, pup won't run on FC6

[Eric]

It seems that whenever I try to run rpm, yum, pirut, or pup on my FC6 
server, it runs partway and then goes into permanent sleep ... can't even 
stop it with HUP or TERM, have to kill it with -9.

I first noticed this behavior four or five days ago but I can't point at 
anything I might have done to cause it.

Any ideas what might have happened or what I can do to fix it?

Unfortunately I guess I can't re-install yum or rpm 'cause I need yum 
and/or rpm to do that... :-(