Strange Shutdowns iMac

[macdon401]

Hi...my iMac 20, 1.8 1.5 G's RAM is shutting down randomly!!

I have to unplug it, then push the pwer button quite a few times until it seems to click in and restart ... and now Spotlight is not working!!

I watched a film last night after working ALL day and let in on ALL night and it didn't shut down having done it early yesterday morning, but this morning it cut out after just 10 minutes??

I have reset the Pram, done permissions, did Maintenance with Butler,
a Apple hardware test and TechTool for what thats worth!!
All say everything is fine??

Can any one help me and let me know what the possible illness is???

Thank you everyone

R

 

[Compile 'em all]

Randomly shutting down is not a good sign. I would opt for calling Apple care immediately.

 

[eji]

Have you seen this?

http://www.apple.com/support/imac/powersupply/repairextension/

Also, have you tried deleting "com.apple.PowerManagement.plist" in >Library>Preferences>SystemConfiguration and then doing an SMU reset?

I installed a Front Row replacement and found (by retracing my steps) that it had corrupted my energy saver prefs, resulting in the random shutdown.

Since deleting these pref files, all's been well (knock on wood!).

SMU reset for iMac G5:

http://docs.info.apple.com/article.html?artnum=301733

Try the .plist deletion and the SMU reset, and if that doesn't work, then you've probably got one of the faulty power supplies (EMCs).