Welcome to the fourms and MC!
I've seen a similar issue recently as well.
As Yaobing suggests, turn off timeshifting as a test.
Also test if you can you change from a working channel to one that doesn't start, as I've found that although some channels won't start I can sometims change to them once playback has started.
Ie. Start Skynews and then use the OSD (Press UP arrow until you see the channel name and he New/Next info and then use LEFT/RIGHT to select a BBC channel, then press ENTER). Will it change channels to the BBC channel then... if not, try another change to a different channel.
Richard