From a few threads I've looked at, it seems this is the current limit, due to the in-game achieve that unlocks the Fireman's Boots, not being in the unlocks in the menu. You can get the boots after meeting the requirements, but the unlock doesn't show in Scores and Unlockables > Achievements. So, can't get to 100%. I have everything done, except that, unless I'm missing something in the game that doesn't show anywhere in the logs/achievements. I've read a few forums around with people with the same problem, and I know it's not game breaking. But... MY OCD DEMANDS IT. Seeing that 99% there, drives me nuts!