It started all of a sudden, well after I installed the plugin. One day it worked great, the next I ran into problems, and now it's just terrible.
I'm worried about upgrading, however. The last time I tried it (and it was on DreamHost), I tried upgrading from 2.64 to 3.11 (it was the most recent version at the time) and I got locked out of MT - and still haven't managed a way back in (that install uses Berkeley DB, not MySQL). Luckily that was on a site I had just begun working on, but I can't risk something similar with this site.
Either way, there's no rational explanation as to why 3.11 shouldn't be working just fine as it always has until a couple weeks ago. DreamHost doesn't have an answer for me either.
But I appreciate your response, thank you.