Assassins Creed weird problem

I was playing perfectly fine until the memory block 3 where the game freeze for like 5 seconds and goes back to normal whenever i kill or assassinate any target or person , or jumping and falling freeze the game for 5 seconds too, then it will goes back to normal.
I was running bittorrent, msn messenger, firefox background all the time, the game runs perfectly until memory block 3 where the freeze begins, and i found out if i disconnect from the internet, the game runs perfectly without any problems at all, but if i connects back, the freezes come again...help plss

My specs
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E7200 @ 3.16GHz at 1.264v in CPUz ; VID 1.2250 ; 50~53c full load ; 31~34c ambient
2X2GB Corsair DD2 800 XMS2
Asus P5N-D bios ver 801
9600GT 512MB/256bit
iBurst USB Modem
80GB Seagate HDD

I have the exact same problem. Tried to block the access by firewall - it freezes more rarely then, but still freezes some time. It seems the only solution is to disconnect the cable.

Phenom 9550 | ASUS M3N-H/HDMI | Sapphire HD 4770 | Windows 7 build 7201 - 64bit

bump

Thank you for the link