Odd, ours stopped working with 3.5.8 as well even though I updated every line by hand from the diff file for func.php.
For some odd reason, the IP logging mysteriously came back right after I updated our database to handle the room required for recording the IP address, http x forwarded for address, and http client IP address.
Try changing the IP field in the orders table to a larger size. Ours is VARCHAR 128.