As far as i understund it, you need to make sure you uncheck all collision tags that ground units use (not just "ground" - for example units may use "ground" and "unused 09"). but... wait... you are asking about how to remove collision while already in game? I think its a questino for triggers subforum then.
edit:
unless it can be done by some behavior... ok i give up :) im to green myself.
@Rushhour: Go
As far as i understund it, you need to make sure you uncheck all collision tags that ground units use (not just "ground" - for example units may use "ground" and "unused 09"). but... wait... you are asking about how to remove collision while already in game? I think its a questino for triggers subforum then.
edit: unless it can be done by some behavior... ok i give up :) im to green myself.