update returns 1, but no changes have been made

I have been trying to update a table -- the update statement returns 1
indicating that one row has been updated, but no changes were made.

This is happening on two servers:

1.my development server, running Postgres 7.0.3, RedHat 7.1
2.soon-to-be production server running Postgres 7.1.3, RedHat 6.2

Could I have a deadlock? Something else?

What should I be looking for?

Thanks.

JT
________________________________________
James Thornton, http://jamesthornton.com