If your scheduled tasks aren't working
I have seen some problems over at vbulletin.com about some scheduled tasks not running. Here is one possible fix.
If you are running an upgraded board, go to your scheduled tasks manager. Remove any scheduled tasks that are not installed by jelsoft and were not installed with a 3.5 modification.
The default ones that come with vbulletin are:
Daily Digest
Subscriptions
Daily Statistics Log
Event Reminder
Thread Views 07-10-2005
Hourly Cleanup #1
Attachment Views
Restore Temporarily Banned Users
Hourly Cleanup
User Promotions
Weekly Digest
Happy Birthday Email
One 3.5 mod I know of that adds one is my Velocity Modification.
If you are a 3.5 mod author and have created a mod that has an updated scheduled task, please let me know and I shall add it to this list.