I've played BG1 and 2 so thought I know how to disarm traps with a thief. However I can't seem to do it with IWD2! I have a thiefling (level 4, 12 Remove trap). I search, find my trap and hit the "Thieving" button. When I hover over the trap it turns into the remove trap icon but it is grey (and this seems to happen to all traps). I've tried taking my leather armour off but that doesn't seem to matter.
No idea. That works for me. Sometimes it might go a bit funny and you go out and come back in again then it works. A 12 in Disarm Traps should be enough for most traps. Which trap in particular are you trying to disarm? Most of them are lame anyway, just charge on through and heal afterwards.