Sounds like you were trying to look at one of the channels in the range 225 to 248 ish, these channels are not suitable for the 9200 and as you have found, lock it up. Switch off at the mains, wait a minute and switch back on. As soon as you can and very quickly change to say BBC1 and if you’re quick enough the 9200 might switch to BBC1. If you can’t get it to do this then switch off at the mains again and remove the aerial, after a minute switch back on and you should now at your leasure be able to switch to BBC1 (or any other channel not in the offending range), shut down to standby, switch off at the mains and reconnect the aerial. Once you’ve got the 9200 running again go to Edit Channels in the menu and delete all the channels in the range mentioned above so you don’t acccidentally select one again.

Note: Strictly speaking you should remove the mains plug before disconnecting / reconnecting the aerial.