Hey guys,
If you have the problem below:
http://www.youtube.com/watch?v=M-QyQVS0pD8

This MIGHT (I repeat- MIGHT) be a solution, if you run steam but bought a retail version of the game:
Add Crysis exe as a non-steam game.
Make sure you have forwarded all the ports listed in the manual.

Once I've done this, I haven't experienced any in-game disconnects so far (joining 6-7 servers). But let me know (or let all of us know) because if this IS the problem to those server disconnects for those experiencing it, this might be the solution.