Deadlock detected

Hello,

  I am getting a few of these errors in my web logs and didn't know what I could do to stop it.

NOTICE:  Deadlock detected -- See the lock(l) manual page for a possible cause.

Error in query "UPDATE <table> SET <field> = <value> WHERE <field2> = <value2>" : ERROR:  WaitOnLock: error on wakeup -
Abortingthis transaction 

Is this due to the hash index on field2 or due to the has index in general?  I read in the mailing archive back in '98
(referringto v6.5) that hash index were bad, is this still the case and should I switch to btree?  I have tried to wrap
theupdate statement with BEGIN; <statement>; END; and get the same results. 

System:
  Linux: 2.2.18
  PostgreSQL: 7.0.3
  gcc: 2.95.2
  libc-2.1.3

Thanks,

Brian

BTW, on a different table I get this warning ever time I vacuum the database. It doesn't seem to cause a problem, but
didn'tknow how to get rid of it.   

NOTICE:  Index <indexname>: NUMBER OF INDEX' TUPLES (214) IS NOT THE SAME AS HEAP' (215).
    Recreate the index.