Serious problem with my postgres

Hi guys,

After a crash and several restarts this morning, my postgres 7.2.1 is
running very oddly.

Every time you execute a query it basially takes forever. Some of them
actually do take forever. eg: "select * from users" just hangs forever. As
people use the site all available postgres slots are taken up by various
random queries until the max backends is reached. The requests cannot be
cancelled within psql, etc.

The processes are hanging in semwait or sbwait or biord states, but mostly
sbwait. Restarts don't help. Reboots don't help. There's nothing in the
logs. What the heck is going on?

Chris