deadlock on simple update

Hello,
I have 8.4.2. I'm getting deadlock when multiple processes try to update
a table. Strange is it is a simple table with no triggers firing etc.
Just an id and a numerical field to update. So I'm at odds as to what
could cause the deadlock?

  DETAIL:  Process 8253 waits for ShareLock on transaction 7001023;
blocked by process 8230.
        Process 8230 waits for ExclusiveLock on tuple (17,269) of
relation 17544 of database 16417; blocked by process 8226.
        Process 8226 waits for ShareLock on transaction 7000961; blocked
by process 8253.
        Process 8253:
        UPDATE statistics SET count = count + 1 WHERE ArticleID=$1 AND
Language=$2

        Process 8230:
        UPDATE statistics SET count = count + 1 WHERE ArticleID=$1 AND
Language=$2

       Process 8226:
       UPDATE statistics SET count = count + 1 WHERE ArticleID=$1 AND
Language=$2

  HINT:  See server log for query details.
  STATEMENT:
       UPDATE statistics SET count = count + 1 WHERE ArticleID=$1 AND
Language=$2

  ERROR:  current transaction is aborted, commands ignored until end of
transaction block