As posted previously in this thread, i have the exact same problem as loady, & the modem was removed a couple of weeks ago, so that isn't the problem.
I thought it might be a signal problem (i have a 3 way splitter), so i removed the splitter & put the main feed into the dbox & still get the same problem, works fine for so long, usually around 15 mins, then freezes, i turn the channel over & get the Error channel not availiable message, when the box is rebooted the channels are back.
I've put the old image i was using back on (sportster 1.76 3) & don't get any of the problems listed above, the only problem i do get is on the odd occasion a channel will freeze, but corrects itself after 1 or 2 seconds.