Cellular Data Network Gone - How to get Tethering working

Hi there,

I have an iPhone 3G in which I installed the latest developer's release 3.0GM.
As a result the "Cellular Data Network" options disappeared.

I've managed to update the carrier settings so as to get the menu back, even enabled MMS and got the option for tethering.

So I enabled tethering and Leopard picked it up creating a new connection "Ethernet Adaptor (en3)" under "Network".

However, even with the iPhone connected via USB, I get a Status: "Cable Unplugged".

Is there any way to maybe "reset" and have Leopard detect it again or something?

I'm not on AT&T, rather on T-Mobile in Greece (Cosmote).

Thanks in advance!