Here is an interesting one for the guru's out there…

Following on from this discussion, our RevA G5 iMac randomly shuts down for no apparent reason.
I have to take it to Brisbane because there are no Apple Authorised techs on the Sunshine Coast (that I can find anyway), and because I work 10-12 hours a day, I don't really have a lot of time to get down there.

My Missus plays on Pogo a fair bit and has to use Safari (not sure why, but she said it doesn't work that well in FF) and she commented to me the other day that it never ever crashes while playing Pogo in Safari. For everything else she uses FF as her browser of choice, because she doesn't really like Safari all that much.

After that comment, I got her to start using Safari for a few days and she has not had one shut-down yet. She decided to open FF while surfing in Safari (FF just sitting in the background) and had her first shutdown all since beginning this exercise. Tried just using FF for a while and starting to get shutdowns again

After doing a few different things we have come to the conclusion that Firefox is the main culprit here. Why? I have no idea

FF is latest revision. Mac is on 10.4.10 with all security updates etc. but this has been happening for quite a while.

Anyone got an opinion here?

Can you try these things and post back what happens

Try using disk utility to check the HD for errors these I have found cause some strange issues.

Check permissions to see if there are any problems.

Also which version of FireFox are you using?

I am running a Rev A iMac G5 anf Firefox 2.0.0.6 and no sudden shutdowns to speak of.

more likely, look at disabling the FF add-ons one by one.

Already thought of that - she doesn't have any installed

Does the iMac display any other strange things like shakey screen at startup?

Does it suddenly shutdown at other times for no apparent reason?

I have had the power supply and logic board replaced 4 times so far and I was seeing these sudden shutdowns and shakey screen.

Do you do any other CPU "intensive" work on it? Perhaps Firefox is hungrier than Safari, and when FF opens, the temp inside your computer goes up, causing it to shut down? I don't know really, just another possibility

I have another ..

obscure maybe but possible indeed.

Available Disk Space.

FF may require more than Safari.

@ Goodbye: No she only uses it for web and email, iphoto & itunes. not much really. Kids play some kids games and stuff like that but it never shuts down then - only when using FF.

@ Rob05: No shakey screens, and only seems to shut down when surfing in FF

@ AusMac: Available disck space is just under 30GB so I don't think will have anything to do with it.

Just Verified Disc and it passed no problems
Verified permissions and came up with 3 small problems so am repairing those now. (thought 3 was pretty good seeing as it hasn't been done for over a year (manually anway))

Thanks for the suggestions guys

Can you go into Activity Viewer and see what CPU usage Firefox is using.

Also is it the latest version of Firefox 2.0.0.6 which is much better than previous versions.

Also get Onyx 1.8.2 and do a deep cache clean and remove any temporary files this helps.

Also open FontBook and check for duplicate fonts these cause strange issues.

Also whilst using ony run all the cron scripts and alike this will also be a big help.

it is a good idea to allow Firefox to automatically update itself.
I believe Rob was referring to Onyx http://www.titanium.free.fr/

Not possible. Unless you are getting crazy panics (which should be logged), FireFox just can't do that.

It's going to be power supply, just like all the other shitty power supplies in Rev A iMacs.

EDIT: If you feel game, you could open up the back (won't void warranty), and check for leaking capacitors on the logic board. Not going to tell you much, but should be also covered by the repair program should you choose to take it in.

Hi all,
I have been out most of the day and will be heading out again shortly. I will try a few suggestions and report back tomorrow.

Spot on. Thanks, Jedda.

I'd want to see crash logs and the System.log before I'd guess at anything.

+1 here also, but you may want to try to first maybe back up the folder located ~/user/Library/Application Support/Firefox and if one is there also ~/user/Library/Application Support/FullCircle (not sure where this one came from maybe an old version test install). After backing them up then move them to trash.

There may also be a remnant of org.mozilla.firefox.plist some where but I think they moved it all to the application support folder instead of preferences now. move it to trash also.

Move the actual Firefox application also to trash. Don't empty it yet.

Best to reboot incase memory has cached something in reference to the location of above folders and files.

After reboot grab a fresh copy of firefox from their site and reinstall. Test and see.

Could be you have something corrupted in any one of the current install. you can reimport the book marks later long as you have not emptied trash or just recreate them again as needed,

BTW if you have an y passwords for anything make sure you know what they are incase you need them to relog on to sites etc.

There was also a recent update to Firefox that covered some security problems which may also be part of the problem.