Comment flooding problem – PHP5 and IIS6

I am running WordPress 1.5.2 on IIS6 (Windows 2003 server) using PHP5 and MySql.

I had been using WordPress with PHP4 without trouble for quite a while. After updating to PHP5, the comment flood prevention began failing for every comment post with the message “Sorry, you can only post a new comment once every 15 seconds. Slow down cowboy.”

I had to comment out the entire “//Simple flood-prevention” snippet in the functions-post.php to get comments working. There seems to have been previous bugs related to this issue, but they also seem to have been resolved in the 1.5 release.

Any help would be greatly appreciated, thank you!