WSUS - how to stop SQLexception.errors?

I've got a WSUS 2.0 server that is just spinning with two types of errors/warnings:

Unable insert update c660e123-bd67-4245-bf82-1459f5e7caeb/110 ... 
...Syntax error converting datetime from character string.

and

Unable insert update c3a2af20-d3c1-4621-a09a-7c83700a6fd1/110 ...
...Some update revisions referred to in XML do not exist in the database 

The SoftwareDistribution log is filling up with errors like this and rolling over. It takes 8 minutes to fill the log and start over (the log is set to the default size, 20KB), which is enough time to do the list and start over 2 or 3 times. It looks like the task spins on the assumption that there is a precedence error.

SQL Server is blocking one core of the dual-core server, and I have to disable the WSUS tasks to ensure that the server remains responsive.

So, any idea how to fix this behaviour?