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Usage of MTCategoryLabel without container tag produces no error message. It will act as if the page is being rebuilt, but produces no output.

In my own case, I'd mistakenly used it as the page title.

Thanks for this post. I spent several hours the other night fighting with this and became incredibly frustrated with my inability to create category archives in an otherwise perfectly sound MT install.

Sure, it was my mistake in using the tag improperly, but boy, an error mesage sure would have saved me some grief

Same problem here -- wasted at least an hour figuring it out.....

You may want to take a look at this post, where I describe a bug that causes MT to silently fail when there's a problem building archive templates, and how to fix the bug (2 edits in lib/MT.pm).