Copy/pasted from the thread on xbox.com:
I just counted up my gold medals, and I've got 42 of them - 40 in Awakening and 2 in Borderlands - but no achievement. Rather disappointed because I was hoping to 200 this one tonight.
I looked around and some folks on your official forums said (to someone else) that you need to clear every challenge mode on every map to get the achievement, which leaves me scratching my head as to why the description specifies 40.
Some people, however, specifically claim that relaxed, practice, 20k challenge, etc count toward this total, in which case it would seem I've fallen victim to one of those "everybody else can get it but not me for no apparent reason" achievement glitches.
Could you perhaps clarify anything I might be misunderstanding? Are there any game modes at all that don't count? Missions that don't count? Anything?