[Thunderbird8]

Does the "last run" time change at all? It sounds like the task system itself isn't functioning, which can be for a few reasons that I've seen in these forums.

First off, the footer template. Can you find these lines?

<!-- Do not remove cronimage or your scheduled tasks will cease to function -->
{vb:raw cronimage}
<!-- Do not remove cronimage or your scheduled tasks will cease to function -->

If not, there's your problem. It's located between the Powered by vBulletin and the copyright lines.

I remember seeing a thread either here or on vb.com by someone who started using a page caching service on their forum, which killed the scheduled tasks. The reason that happens is because the {vb:raw cronimage} generates a 1x1 image with a random number on the end. If this number isn't changing, the scheduled task system will think it was just a cached page being pulled, and won't run any tasks.