episode achievments not unlocking?

[xX King Mik3 Xx]

i finished episode one, stood on the teleporter platform and got killed by the enemies and a random message appeared on my screen, i was sent to the menu with no achievment. Can anybody help?

[Pheonix_Assassin]

Re-load your gamesave and try again =)

Thats all i can say =)

Remember to always save often

[itz s l i t]

if it was mp then ur out of luck if it was single player make sure ur difficulty was set high enough