Problem with uppgrading nw 4.11 to 6.5

Has anyone had the same problem, i?m trying to uppgrade an existing netware 4.11 to Netware 6.5.
I can see the network and the servers from both nw 4.11 and 6.5, but i can?t connect to the nds tree. I have turn the ip off on the nw 6.5 server, and it?s still work. The netware 4 server is running ipx/spx tcp/ip and netwareIP. Will be greatfull if any has a tip that could be usefull.