Well spotted Sue_Aitch.
I confirm your problem on my HD500 - I have yet to update the software to the latest version.
I have found, like you, that the Red Button Menu Systems (Blue Button) for 302 (Red Button 2) and Red Button HD are not working as expected and if an option is selected it leaves you with a blank screen and no sound, most times. However, sometimes the menu system did work - perhaps as a result of the multiple tests I did.
"Exit to BBC1" from 302 took the box to BBC1 HD which is a bit surprising.
On my HD500, this fault situation was easily corrected by using the Channel Up/Down Button or entering a Channel Number from 301/302/303. And, for exit, the problem can also be avoided by using the Swap Channel Button (returns to previous channel) or as above.
Multiple use of the Swap Channel Button can recover the box from the fault situation but I also found that, when arriving at BBC1 HD, the box refused to accept a channel number but would respond to a Channel Up/Down command.
It may be that these issues are related to the iPlayer problem so I will be updating my box and will repeat my tests.
Martin