You'll need xterm and becomeroot installed. If not, then this could be tricky. Assuming you have this installed already:
- Start xterm
- sudo gainroot
- dpkg --purge mediastreamer

If that worked, you're set. If not, then you have to rewind back to the situation before you started installing mediastreamer (there's only one rewind, that's why you need xterm etc. already).
- start xterm
- sudo gainroot
- cd /var/lib/dpkg
- mv status status.bad
- cp status-old status
- exit
- exit
If that worked, then the system will believe that mediastreamer (or the latest you installed) isn't installed, even though there will probably be remnants and files here and there. If you figured out what you did wrong to get the aborted installation then the best thing to do now is to install it again, even if you should just want to delete it right away.

If you don't have xterm and becomeroot then you might have to settle for reflashing and reinstalling (make backup first).