Thanks for the information, Husse, and Merlwiz,
As I've found over the weekend, my modem started to exhibit intermittent connectivity problems, and I had to buy a new one yesterday. So I wonder if something went FUBAR, and the connection dropped during the middle of installation/removal. I uninstalled MythTV through Synaptic, and haven't had a problem with it before, but there's always a first time for everything.
I don't use any special themes. The most I have done in the past is change the desktop wallpaper. Anything that doesn't appear to be fairly straight-forward, or seems to have had many installation complaints, I don't even look at. I didn't see any major issues with MythTV, so gave it a shot.
I'll do the recovery mode and fsck. I didn't think that Thunderbird uses a database, but as with many things, there are things running in the background that we don't always see. (Shudders at the remembrance of Windows background processes
I looked through the .mozilla-thunderbird directory, but only found that one profile. I'll see if I can find another profile that is hiding out.
As I always say, everything happens for a reason, even if we may not always understand at the time the reason why something happens.