I have a 5555 and a t608. I've forgotten the exact steps I used to pair them; I do know you have to set it up as a dun connection. There is a t608 forum on
www.sprintpcsinfo.com, and there are at least a couple of threads from back in January that give step by step instructions on setting up internet access. It seems to have taken everyone several tries before it worked.
I've never tried to synchronize anything; I just use it for internet access.