I had been updating this weblog with the Movable Type 4 betas, all the way up through the final release, MT 4.01. Even in the latest version, I was consistently getting an error message whenever I tried to update an entry that had already been published:

Error On Line 1030: Can't call method "date_based" on unblessed reference

If you're re-publishing a single entry, the entry publishes anyway. If you're re-publishing multiple entries, however, it stops after publishing one entry. So it's annoying.

It looks like this problem is related to "ExtensibleArchives," a set of plugins that were once included with Movable Type by default. Removing the mt/plugins/ExtensibleArchives directory causes the problem to go away.

The ExtensibleArchives plugins are not present in the latest MT 4.01, so I'm guessing only people that followed along with the betas have these files and are affected. I don't have time to look into it further.