I found out the hard way yesterday not to try beta firmware on my iPhone yesterday. 

I had read a lot about the new features of the new firmware 3.0 so decided to try it out after I found it was easy to come by.  I went through the normal process for the upgrade and every went ok.  iPhone rebooted and came up.  I connected to itunes to activate and found out that it had expired. :(

Back to the old version (2.2.1). Well that wasn't as easy as I thought it was going to be. I did a restore in itunes to version 2.2.1 (Hold Shift + Click Restore and specify firmware 2.2.1).  Initially everything went well but then before the iPhone started up again itunes had an error 1013.  I tried almost everything.  I went through heaps of forums, tried other computers, tried my mates firmware with all the same results.  Eventually I mixed different options and methods and came up with this solution.

Connect to itunes and restore to latest firmware.
Once firmware upload is finished it comes up with error 1031.
close itunes and start quickpwn.
It will say about holding home and pwr for 15 seconds.  Complete this.
Once it comes up asking to connect to itunes, close quickpwn and connect to itunes.  It will unlock and activate it.
Now you are ready to use quickpwn again to jailbreak (If Wanted)

nb If you get a firmware string error you need to restore or setup as new through itunes

for the latest version of quickpwn go here

Hope this will help some of you.  Hit me back if it does.

Cheers,

Daniel