I have had something similar recently.
After converting maybe 50 youtube video avi files to large-size sansa avi files, I tried one particular one and it would always just “stop working”. I’d Add Media (only the one file) and the whole Media Converter program would jsut disappear off my screen! finally, after about 5 tries, my computer went to blue screen of death with a whole lot of scary messages about Stop Error and how serious it was. I sent the Error Message to Microsoft where they will, I’m sure, give it top priority in their “round file”.
Anwyay, I rebooted and apprarently there are no lasting issues, I removed SMC from my hard drive and re-downloaded and installed it.
It converts the file without any problem now. but the very next one I tried to convert, it just stopped working. It did not disappear liek before, it just totally froze itself with semi-visible graphics (it looks like you took an exacto to the SMC screen and left hoels in it here and there). Can’t even right-mouse-click “close”…just totally frozen. All other apps working fine.
So reboot the whole machine again.
It is just a very odd and glitchy app; there’s no way around that. Maybe we just have to see it as a Freebie. Worth about what you pay for it.