I had a similar problem with my old Nokia 5800 not being able to show contacts on my Navman. Other phones seemed to work ok and I found that if I went back to my contacts on the phone and enabled them (each ended up with a tick) and then went through the process of setting up contacts it all worked well.
Clearly, I can't tell if it's a similar solution for your situation, but it took me ages to figure it out since nobody else seemed to have the problem.
Best of luck... you'll probably find that the solution is pretty straight forward (when you know!!)
