I might be wrong, but I believe the only way you can downgrade back to 4 is if you have a backup dump of your entire mySQL 4 that you can manually restore to the server. I honestly would not know how to go about doing the downgrade/restore, but I made sure to have a backup of mySQL 4 before upgrading to 4.1 (by having my backup config in WHM set to backup "Per account and Entire MySQL Directory to a separate drive). If you have your backup configured like that in WHM, then I *think* you should have a backup copy of your old mySQL. But again, I wouldn't know the exact steps to restore/downgrade it, so hopefully one of the experts here on the board can explain that part to you.