Well, ive tried it on three computers and succes on all three accounts. Ive found that if you go into your Buy/Sell menu and sell and then buy back all you "Primary" wepons. In onther words, just start at the top of the wepons listing, for me assault rifles are at the top. If you have 5 on hand, sell them, and then you can imidietly buy the 5 back. Repeat this will all your primary weapons, dont have to mess with ammo ar anything else, just the wepons. So far this has gotten rid of any lag, both in the arming menu and during the missions. Really not sure why this works, but so far it does.