My G5 seemed to be running just fine before I went to America but when I came back it wouldn't start up and I got a grey screen with the prohibitory sign. I've tried resetting the SMU, PRAM & NVRAM as well as reseating the RAM - I've also erased the hard drive & reinstalled the OS and although it started up ok after the reinstall, the next day I got the same grey screen & prohibitory sign. Anyone have any ideas what else I can try? Or if it's hardware, what hardware it's likely to be? I have Apple Care for another 6 months or so but unfortunately I'm not covered in Cyprus (despite the fact that they're in Europe, they're only European when it suits them ) so I might have to lug it back to the UK next time I fly out there but I really don't want to be doing that ... the damn thing is so heavy!!

My husband says it's probably the hard drive going bad.

can you start it with the original DVD that came with it?

It struggled to boot up from the dvd and it took me a few tries doing different things/pressing different keys & resetting stuff to get it to start from the dvd. Since doing the "erase & install" I haven't tried booting from the dvd again coz I thought if it was the OS then the reinstall should have fixed any issues, right? Any point in using the dvd & going into disk utility and repairing permissions/disk again, you think?

Try booting in single-user mode by holding down the Command (Apple) key and the S key after you hear the startup chime. You will then see text messages on your screen as it starts up. This should at least show you what file is causing the issue and you can research it further.

More info here (not sure if the US keyboard layout thing applies to you or not):
http://docs.info.apple.com/article.html?artnum=106388

If you do the verbose mode thing, it should at least tell you which if the files listed on this page is the broken one.
http://docs.info.apple.com/article.html?artnum=106805

Hope this helps!

have you tried using a fresh hard drive? this has me as stumped as you are, but either a component or a file is causing the problem.... you may as well try ruling out the component part of it.

Try Disk Warrior. My New HD did that and I couldn't figure it out...turned out to be a bad HD but Disk Warrior got it to run to find that out...it will test the HD and startup system. It's saved my butt more times than I care to mention. Well worth the $99US.

before you go wasting money on hard drives, ram, and what not..

Boot into hardware test with the CD that came with it.. run the tests and we'll go from there.

Sounds like the NVR battery is dying - when you book up you temporarily charge it up, but it loses the settings again when you turn it off. It's worth trying to replace 1st before you go shipping it anywhere, shouldn't cost you the earth - two to five quid tops...

Apple's Battery Replacement Instructions.

try disconnecting the mouse and keyboard and possibly adding another one. When I moved we determined my keyboard was damaged and was sending out signals to the G5 which was preventing it from booting. When I took it to the apple store it booted fine every time with a different keyboard/mouse - but then when mine were plugged in it wouldn't boot. Simple simple fix big headache lol.

try disconnecting the mouse and keyboard and possibly adding another one. When I moved we determined my keyboard was damaged and was sending out signals to the G5 which was preventing it from booting. When I took it to the apple store it booted fine every time with a different keyboard/mouse - but then when mine were plugged in it wouldn't boot. Simple simple fix big headache lol.

I think this is your problem.

? I shouldn't have gone to America?!!

Thanks for all the advice - I haven't had a chance to do anything with the computer yet (I've commandeered Paul's computer so I can get some work done!) but I'll try some suggestions out tomorrow.

The problems is cyprus.

This happened to me a lot when i moved to moldova aka russia. the reasons can be the power difference, the bad quality of disks which have no made both my mac drives un usable however i think its a hard drive error as twice my macbook pros hd has crashed and each time it gave the same errors. its definately the hardware as refreshing your hd and installing the soft again should clean any soft error, so my best bet is the hd drive, im going to PM you a few friends i have working in apple tech centers in europe and they should be able to help.

Ok, so I managed to get the damn thing started and erase the hard drive & reinstall the software and it started back up like a dream - this was about 3 weeks ago now. The next day, it wouldn't restart I tried a couple of times and nothing so I resigned myself to the fact that I'd be shipping it back to the UK to get it fixed under warranty. Anyways, today I thought I'd see if it would start and you wouldn't believe it but it started first time and even did the start-up chime which it wasn't doing previously I seriously don't get it.

Anyways, I'm running the Apple Hardware test on it right now and wanted to know how reliable the results are on that? I read somewhere that you should put it on loop because it may not find a fault till it's run like 10 times (which really doesn't inspire me with much confidence in the test!) So far, it's gone through the airport, logic board & mass storage and they've all "passed" but it still has the memory to go through and video device.