iMac acting weird, doing soft reboots randomly

[dveiga]

Hey everyone,

I own a late 09 iMac 27", had 8GB of ram (4gb apple and 4gb owc). I don't have warranty anymore, and as of lately my Mac has been acting wierd.

I'm not sure if its related to memory issues, but once in a while for the past 2 months, it acts like its shutting down (blue screen) but then the desktop comes back up with all my apps closed out... as if I had just rebooted. It doesn't physically reboot tho.

I'm a web developer so I have lots of apps open, firefox is the main one and due to its memory leaks sometimes hovers around 2GB of ram being used. Most of the time my free ram is under 500MB, but inactive is always typically 1.5GB +

Anyone know what it can possibly be?

 

[Makosuke]

The symptom you're seeing is a Loginwindow crash; that's the process that essentially handles your current user login, and which spawns all your running apps. If it crashes, you get immediately dumped back to the login screen, as if you had selected "Log out" from the Apple menu, except without the chance to save anything. I believe if you have automatic login enabled--which you presumably do--you will then get automatically logged back on, as you're seeing.

Once in a blue moon, that might happen--I've seen maybe three since the advent of OSX. As regularly as you're seeing, it's a symptom of some major problem. If you're lucky, it's just software.

Did you recently install anything system-level--hacks, utilities, or modifications? If not, maybe there's some sort of disk corruption that's causing crashes and can be fixed by booting from the OS install disc and running Disk Utility to repair it. Slightly worse would be a corrupt OS install somehow, in which case you'd need to reinstall the OS (but will be able to save your user settings)--just time consuming.

If you're unlucky, you have a hardware problem. Most obvious would be a failing hard drive, but that would usually have other symptoms--most often periodic system hangs or maybe application crashes. Bad RAM could also do this, although I'd expect other apps to crash randomly as well; you could diagnose this by removing half the RAM and seeing if it goes away, then if not putting it back and trying the other half. Worst of all would be a failing motherboard, which is very expensive to replace since it's out of warranty.

Try finding the discs that came with the computer and booting into the Apple Hardware Test and see if it finds anything--there are a lot of times it won't find a hardware problem even though one exists, but it's worth a shot to see if it shows anything (particularly bad RAM--be sure to do the "long" test).