PostgreSQL 8.4 hangs on create table, reindex
if it is hanging forever, without significant CPU or IO activity, it is waiting on a lock.  The two things I would try here would be checking pg_stat_activity to see if something else is running that might conflict.  Maybe someone else has an open transaction in another window that has conflicting locks?  Then I would check pg_locks.

Then I would look at pg_terminate_backend() on the offending process and try again.

However create table is a weird one.  I can't think, off-hand, of any case where this should be blocked.  Wondering what kinds of locks are required for this and under what circumstances they can conflict.

Edit:  It occurs to me that the locking could be lower level than Pg-level locks and involve semaphores against shmem segments.  But if that's the case your best bet is to take this up with Amazon since it would be more of an OS issue.