Sounds like something is consuming a lot of CPU and causing the device (not the touchscreen) to become unresponsive... most likely culprit is metalayer-crawler and a corrupt SD/MMC card filesystem (or a recursive symlink) which makes it go nuts. Searcht the forum for metalayer-crawler and you'll find some useful posts which should help deal with it.

Alternatively run top in a remote session over wifi and see what is running on your device when you experience this problem.