Can't get perfect game?

[Vex_M]

Weird bug or something? I just recently got all (I even checked multiple times) the Half life 2 achievements. Though, steam claims I've got 32/33, making me stuck at 96%. I even entered the game and clicked "hide achieved" in-game, and nothing popped up (meaning that I really do have all the achievements). This isn't THAT importrant to me, though I'd like to finally get a perfect game xD
Any help'd be appretiated

[Bruno]

You're apparently missing "Singularity Collapse", which is a story related achievement..
Weird bug.
Try loading a save right before you blow up the citadel's reactor core and finish the game from there.

[Vex_M]

Thanks, I'll try that. I would've noted that I'm missing it, though the freakin' game doesn't even show that I'm missing the achievement.
EDIT:
Okay I've got all the achievements, thanks for that a lot. The weird thing is that most of the time the game said I already had 100% achievements, and steam did too.