2 player via Wifi

[icombat]

I am currently developing a game that has 2 player over wifi - having some problems with getting different models to work smoothly over wifi together (2G paired with 3G iPhone or Touch paired with 2G for example). When models are mixed the resulting image is jumpy and sometimes completely out of sync with the other device.

Any ideas why this could be happening? Any suggestions? Devices work well when they are the same generation / model. Thanks for your help!