When I try to publish entries, they are saved to the MT database, but I get the following error message and they fail to appear on the main site: "failed on entry '': Build error in template 'Export Template': Error in tag: You used an MTEntryDate tag without a date context set up." I'm guessing that my site has (yet again) become corrupted, but I was wondering if there might be some way to fix this other than rebuilding the entire site again? Thank you.

Unless you've got an entry without a date somewhere, or the tag is being used outside of an MTEntries container, that error message is fast developing a reputation as a indicator of database corruption.

Are you using Berkeley, I assume?

Yes, I am using Berkeley. I'm going to try and install using MySQL, and see how that works. I'm not at all familiar with it, so I've gone with Berkeley for comfort, but obviously that isn't working for me, as this is not the first time the system has become corrupted. Thank you for the confirmation.