I just hit level 20 in MP, and i have been trying to upgrade my armor enhance and stealth enhance, only to find that my counters (#/150) have reset. I was so close to unlocking the secondary upgrades to stealth and armor enchance only to find i have to get all those god damn kills over again. Im not sure if anyone else is having this problem but it kinda svcks.
Also i found you can unlock attachments in private matches and re unlock another attachment in MP. My example is i had 49/50 kills on my Grendle, so i only needed one more kill to get an attachment for it. I went into a private match hosted by a friend, killed him and once the game was over i got the attachment... however my counter still showed i had 49 kills, but rather than 49/50 it was 49/100. Then i went into multiplayer, got a kill with my grendle and unlocked another attachment, so i now have a silencer and an assault scope on my grendle with only 50 kills. I am still trying to figure out the circumstances that help unlock attachments in private matches that carry over to multiplayer, but what i have deduced is that you cannot get attachments when you are hosting a private match, only when someone else is.
If anyone else has these problems please reply so i know its not just me

P.S. Crysis 2 is awesome