Isn't this the 'Thinks I am recording' bug, which is mentioned in FAQ #81?

Yes, this is mentioned in FAQ #81. I will look into adding some posts from this thread to pad out the explaination a bit. Also adding a reference to the 'PIP not available' message.

I have also encountered this problem.
The symptom is that although the standby button is pressed on the remote the machine goes into a state where it starts immediately next time the on/off button is pressed on the remote. The easiest way of telling that this has happened is that the little clock symbol on the display does not illuminate although the machine is showing the time as it would normally in stand-by. On starting the EPG is fully populated and recording and play back seem to operate correctly (although I haven't tried 2 simultaneous recordings) but once in this state use of PIP is not possible and the message is given that this is prohibited during recording (although no recording is taking place). I've been suffering from my machine intermittently not switching off properly but I hadn't connected it with PIP as I very rarely use that facility. I encountered the same symptoms again last night and when I just checked I'm getting the same message that PIP is unavailable during recording. I'm sure that it is connected with 2 recordings starting simultaneously - in my case I had BBC1 and BBC4 both set to record starting at 7pm. As it happened I was able to watch the BBC4 transmission live but used the red dot to see additional info so it switched to 303 (I think). That presumably meets the theory of 2 recordings and one live transmission all from the same MUX? I've reported this problem to Humax in case they think it was fixed by the software update.

BBC One is on a different MUX to the BBCi Video streams(+303) and BBC Four.