Originally Posted by TigerSparky
A little late, but it will not clear out all your achievements or your saves. All it will do is clear out any title updates that you downloaded from xbox that you aren't able to remove from your hard drive manually. Here's a little more info on it in case you still need it:
This worked for me. Cleared my Memory Cache on my 360, loaded up the game (did NOT download the update), loaded the Rig level on easy, collected both intels and wham-o, 50G!
I was at 28/30 collected, even though I followed the guide throughout the whole game (played on hard). The intels I had missing were 05 and 08.