Identifying problem with SIM Card use

[Guest alun hove]

I have a replacement Dell Streak (first one was stolen) purchased unlocked from Dell. It does not want to recognise the Orange Mobile Internet SIM Card that I have inserted. In the Settings menu the "Mobile Networks" option is grayed out. Unfortunately I had not attempted to use the SIM Card before activitating the upgrade to 2.2 do I dont know whether there is a physical problem or whether the upgrade to 2.2 has created a software problem. I know the SIM Card is ok as It works in the dongle on the lap top. The previous SIM Card had worked perfectly ok in the previous Streak but am on a replacement SIM Card because the previous one was in the previous Streak when it was stolen.

Is it worth reverting to Factory default to see whether the 2.2 upgrade is causing the problem (although the previous Streak had been up graded to 2.2 also or is it more likely to be a hardware problem.

Alun