MXit should run on any windows mobile device with a suitable JVM / midlet manager installed. Head over to http://forum.mxit.co.za. I'm sure the guys on the MXit forums will be able to help you out.
My k-jam running mxit fine aswel, though i have a problem. Don't know if its MTN or what but my gprs connection just hangs after a while. It shows its connected but no data up or down