I was wondering if anyone could test this out for me...

I'm currently running 3.0.1 on the iPhone 3G with tethering enabled. I was connected to a computer set up to use the phone for tethering, but had tethering disabled.

I then proceeded to make a phone call, and while on the call hit the home button to bring me to the home screen (This puts the green "Touch to return to call" banner at the top, where the blue tethering one normally goes). I then navigated to settings and flicked tethering on. Boom.. Instant Hard reset.

Can anyone check and see if this happens to them? And if not, what banner gets displayed at the top when both tethering is on and a call is in place outside the phone app? (Presumably just the green banner, as iirc the blue one disappears when on a phone call, even though tethering remains enabled if you have a 3G connection).

you would think the phone call would cancel out tethering for the time you take the call maybe the system had a hiccup and didnt know what to do about it...

how many times can you make this happen?

I was quite surprised when, after I replaced my original 2G iPhone with a shiny new 3GS, and noticed I was able to keep browsing while talking on the voice network! Back on EDGE, either I talked or I use Internet, but not both as of now on 3G.

So I (quite extensively) tested this and while tethering is active, the banner on top is the green one when a voice call is in place. I had not, however, had my phone rebooted as OP relates.