I found the following when I did a diff on wp-includes/functions.php. The 2.0.3 version is on top, the previous version is on bottom:
Starting around line 35 or so in functions.php and continuing for about 5 lines are \${1} in the function call. In the previous version, it was \\1.
Changing the \${1} to \\1, as it was in the previous version fixed things. I’m running PHP 4.1.2.
