I'm experiencing problems too while trying to dial out using OZ 3.5.1 on my 5500. I can set up the PPP connection in the Network Settings app, and can turn on IrDA and discovery to recognize my Nokia 6220. However, when I tell it to Start the connection, it goes through the normal dialing messages ending with "Online" but no IP address is assigned, and the Nokia's GPRS indicator never turns on.
Do I need to manually edit some files, or install another package, etc...? This has just worked since 3.3.5 and the hentges releases, so I'm stumped now.