I also had an issue yesterday too.
I was watching a show and midway decided to record the rest for later, and switched to another channel to watch something else and midway decided to record it as well for later viewing.
After that I started watching a prerecorded show from the list.
About an hour later, only one show was still recording and on the receiver only one red icon was lit.
I tried to switch to live viewing and I kept getting the pop window that no tuners were available and to choose DVR or VOD.
I went back to watch another recorded show until the one that was recording was finished and was then able to go to live TV.