Ubuntu :: Python Based Programs Not Working

I've been using Ubuntu 9.10 fairly regularly on my home computer for a week or two now, dual-booting it with Windows 7. So far I've been quite happy with it, but yesterday something odd happened. I decided to copy all the music I had stored on the Windows partition over to the Ubuntu file system so that I could listen to it there. I have about 16 gigs of music mostly in .mp3 format, so I put the folder on an external hard drive, then logged into Ubuntu and copied it back from the external drive to my Music file.

Once the transfer was done, I opened the Music file and double-clicked on one of the .mp3s at random to play it. When I did this, a window popped up and the first half-second or so of the track played, and then the window closed and it stopped. This happened once or twice more with different .mp3s. The window didn't last long enough for me to get a good idea of what program it was for, but I assume it was Totem, which I hadn't yet run since installing Ubuntu, because according to the Properties->Open With tab of any .mp3 file, that's the default program to use to open .mp3s.

Attempting to run Totem from the Applications menu gives the same result, I later found. Attempting to run Totem from a terminal gave the following error:

andrew@Lovelace-Linux:~$ totem
** (totem:2323): WARNING **: Could not import pygtk
ImportError: No module named pygtk
Segmentation fault

Then, several other programs began having similar issues immediately after I first tried to play a .mp3 yesterday. Specifically, Rhythmbox - which I also hadn't used before, and next tried to use to play the music - will not start at all. Running it from the terminal gives:

andrew@Lovelace-Linux:~$ rhythmbox
** (rhythmbox:2338): CRITICAL **: atk_object_set_name: assertion `name != NULL' failed
** (rhythmbox:2338): CRITICAL **: atk_object_set_name: assertion `name != NULL' failed
(rhythmbox:2338): Rhythmbox-WARNING **: Could not import pygtk
ImportError: No module named pygtk
Segmentation fault

Note that pygtk is again referenced. The weirdest part is that other program that's having this issue, an IM client called emesene, is one that I had been using just fine, without issue, for several sessions previous. Since trying to play that .mp3, it now won't run at all. I tried removing and re-installing emesene, to no avail. Running it from the Terminal gives:

andrew@Lovelace-Linux:~$ emesene
Traceback (most recent call last):
File "/usr/share/emesene/Controller.py", line 21, in <module>
import gtk
ImportError: No module named gtk

This time the missing module is gtk, but I know that emesene is written in Python, which the earlier "pygtk" is perhaps a reference to. Thus, the connecting thread between all these programs, as near as I can tell, is Python.