Postgres processes getting stuck (bug?)

Hi guys,

I had a question. We're running Postgresql 9.0.7 , and all of a sudden we
started seeing unexpected behavior. One table got locked after we ran one
simple INSERT on one test item.
Nothing else was running against that table as far as we know, and the
query is frozen there now. After some time we tried to terminate it
forcefully (pg_terminate_backend), ran that and the return of the command
is "true" but the query still stays on, shows up on pg_stat_activity etc.
Reading from the table is fine, but we believe any other inserts / updates
are not possible.

Restarting the Postgresql server is not an option at this moment, since
it's a production box and another high-demand database is running from that.

Has anyone seen a similar issue (maybe a bug in the 9.0 version ?) where
simple statements don't finish and get locked there and can't be killed by
the pg_terminate_backed ? What is the cause of this ?
Any reasonable way to find out more details on what caused this, how to
prevent it in the future, and how it can be fixed sensitively now ? Thanks !

just fyi, checking the data in the "pg_locks" (for that process that is
frozen), shows a bunch of rows all with the same virtualtransactionid. Only
one of them has the mode of "ExclusiveLock" (the only record there with a
locktype of "virtualxid"), a few have the "RowExclusiveLock" mode and the
vast majority have the "AccessShareLock" mode.

Thanks,
Ciprian