Just tried the iOS beta 7 update OTA on my 3GS.
It’s bricked it and according to a Google search, I’m not the only one.
Trying to restore to the full download from the developers site to see if that works.
Need to use iTunes and the phone in DFU mode to do this.
To save you looking, cos I couldn’t remember how either, Open iTunes – Connect phone using USB, hold down the Home and the Power button for 10 seconds, release the power button but keep hold of the Home button. iTunes will eventually say that a phone has been found in recovery mode etc etc. Download the new update and install from there.
I’ll let you know how I get on.
UPDATE – OK that worked. Beta 7 now in place, even managed to restore my phone form the iCloud backup from last night, so I’ve not lost anything. Well done Apple, just need to get those OTA updates nailed.