When you try to switch channel from one card to another card,if the channel on the second card doesn't receive any signal,My Tv is freezing and instead of "Unable To Start Timeshifting -No Signal "warning,a NullReference exception error is created in MediPortal.log

h4. Steps to Reproduce
First create a "fake channel" for analog or just plug out your analog antenna.Start MediaPortal,go in MyTV and Start Timeshifting on a dvb-t channel,now switch on the "fake" analog channel.MyTv will freeze on the last watched channel without any "Unable To Start Timeshifting -No Signal "warning.

h4. Additional Information
Tested with my hybrid card (dvb-s,dvb-t and analog) so please test with multiple cards too.