Hi Steve
Thats a bummer! Never had or heard of this issue.
Is this just the HDMI input, or does it affect Component, Composte and/or SVHS? Assuming you are routing sources via an AVR or equivalent, have you tried hooking up the PJ directly to a source?
If its just the HDMI, has the cable got pinched, trodden on, or exposed to excessive heat that might have caused damage?
The input settings haven't been altered by somebody ? - I know you can "hide" inputs you are not using from the source list, so might be a freaky occurence.
Has the bulb been recently replaced or the PJ knocked/dropped? might be a faulty connection although I have no experience of fitting a new bulb.
Does the cooling fan staart up and sound OK - not sure if there the pj can sort of shut down of too hot because of insufficient cooling.
You could try speaking to an engineer at Sim2 for advice.
Sorry these ideas are a bit vague, just trying to help!
Good luck!