Personally I rarely get problems with IceTV and when I do a guide update and reboot generally fixes it without the need to reinstall or rescan. This is a known issue with IceTV and lots of us have a scheduled reboot or cycle of MCE immediately following the guide update which generally avoids the problem altogether. As far as system updates go I can only say that I avoid them as much as possible once the machine is stable. I try to keep my tinkering to another PC elsewhere because the stress of being without my MCE is too great!
