I had my host provider upgrade my weblog to Movable Type 4. At first, it looked like connections to the CSS stylesheets were broken, but it turns out that that the public_html/mt-static/themes directory that had the CSS files was replaced with a new one for MT4. Luckily, I had zipped this directory up before the upgrade and copied the zip file somewhere else, so when I restored the directory of the CSS that I use everything went back to normal.
Well, everything except the ability to search through the entries. Attempting to search gives me the message "Publishing results failed: Can't find included template module 'Header'". This discussion of a similar problem tells me to republish the templates, and this Movable Type help page explains how to do this. I worry that this sweeping command will mess up my existing templates in addition to generating the missing ones, and I've already spent too much time on this today, so for now I've commented out the search feature of this blog until I can really make sure that I have everything backed up that needs to be before taking this step.
Blogging about blogging is the one category of my entries here that I actively try to avoid contributing to—it's such a tiresome topic on so many weblogs—but this entry also serves as a bit of post-upgrade regression testing. I'd hate to find out that the upgrade screwed up my feeds after posting something more substantive.