Have you updated your tv to coinside with the switch over? If not that could be the problem. Get a digital tv or a freeview/or other 'box' to fit to tv to get channels back. Are you in UK?...If Yes try here for info/help/post questions/etc:
http://www.frequencycast.co.uk/freeviewadvice.html
Some good links on here that may help you to find answers.
UK ONLY: Check your signal strength here:
http://www.wolfbane.com/cgi-bin/tvd.exe?
fedup68
September 2011
Automatic Answer
We may have found other answers which could help you.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix televisions.