When you got those achievements, did they show up in the style of xbox - green-on-black notification with signature "achievement unlocked' sound?
The reason I ask is because I was experiencing issues with Monopoly not registering my achievements to my xbl gamertag. I noticed that when the achievements were unlocked, they appeared in the style of Monopoly as opposed to the green-on-black xbl color scheme with the recognizable "achievement unlocked" sound. I *think* I wasn't showing up on the leader boards either. I had recently changed my windows live password and I figured that Monopoly had become unlinked from my xbl account (or wasn't linked in the first place). I un-installed and re-downloaded the game and my achievements are now registering to my xbl account. (I did lose my previous progress and achievements, not sure if this loss would happen with other xbl games).