I'm having the same problem here. I'm a relatively new customer (first time poster on DBStalk too

) and have a HR34 and two C31 clients. The service worked flawlessly for the first week, but after that (possibly coinciding with a software update rolled out on Oct 31st) I started having problems with my C31 devices.
When I power the C31 on, it'll show a blank grey screen. I can usually browse the menus, show listings, and guide but the C31 will never play a recorded show or live TV. When it gets in this state, even a full RBR won't resolve the problem. I must reset the HR34 unit before the C31 client will come back.
At first I thought it might have been a defective C31 unit, so I swapped the C31 that I use regularly with the the C31 in the guest bedroom. The second C31 began having that exact same problem though, so I don't think it's a hardware issue.
I've read of other people on a different forum having this same problem. I don't think it's a cabling or bad connection. Like I said, it worked fine for the entire first week. And I'm able to resolve the problem by rebooting the HR34 unit. But it only stays fixed for a day or sometimes less before the C31 units run into the same problem again.
I'm hoping that a future software release will fix this problem. I have no idea if/when a release is planned for these devices? I sympathize with the original poster though. It has been quite annoying to reset the server and lose recordings that are in progress on a daily basis to resolve this grey screen issue on the C31s.