Word Press help

We just tried to upgrade my Word Press to 2.02 but ran into a problem. On the blog home page, we got this inserted on the top of the page; it also showed up on the top of the Word Press ‘manage’ page:

Warning: preg_match(): Compilation failed: nothing to repeat at offset 1 in /home/jarvis/public_html/wp-includes/classes.php on line 1542

This also made the CSS on my home page go wacky; everything went into the large-print edition.

And when I edited a post, it would take the change but go to a 404 page-not-found.

For those of you who posted comments in the last few minutes, they were lost as we downgraded until we get this solved.

Any help much appreciate.