verbs - What is the difference in nuance and usage of the two kanji forms for なおす (naosu), 直す and 治す?

Stolen directly from Grigory M's question in the definition phase:

http://area51.stackexchange.com/proposals/7526?phase=definition

Answer

They both mean "to fix"/"to repair"/"to correct", but 治す is used in the sense of "to heal or cure" ("to fix a disease"). "直す" is used for fixing, not healing.

EDIT: As per Tsuyoshi Ito's correction (confirmed with a bit of googling), I've removed a misleading bit about the object of these verbs.