I have an intermittent grey screen problem when booting my Mac Mini (PPC). I get the grey screen with no Apple logo, and find it impossible to boot in safe mode, single user mode or from Tiger install CD (ie. no response from wireless or wired keyboard).

Generally this happens if the power supply has been disconnected or switched off for some reason (most commonly when moving the Mini from one location to another, eg. when it's been plugged into the TV for watching media then returned to the desktop).

It has happened four times in 18 months. On the first, third and fourth occasions I've taken it in for repair only to have it boot perfectly happily each time. On the third occasion I nevertheless asked the repair people to run a full diagnostic which returned minor, fixable errors on the hard drive but no other problems. On the second occasion I simply left it for a weekend and when I booted up on the Monday, it was fine.

On one occasion I tried booting up when attached to the TV to see if it was simply an issue with the monitor, but got a black screen. So could it possibly be a problem with the DVI-VGA adapter?

The other strange thing is that on the most recent occasion I couldn't eject the Tiger install CD by holding down the mouse button on startup - if it was merely a display issue then surely this wouldn't be the case?

Given that the machine has corrected itself each time, the problem seems a benign one; it's frustrating, however, to live with such uncertainy! I wonder if anyone else had heard of or experienced similar problems.

Could be a problem with the power in your house. As a general rule, if it works in the shop perfectly, I always end up suspecting something at home. Have you experimented with it connected to different power points in your house?

Yep, and not only that, I've had the same problem in two different houses now