Freezing/stalling issues on my Mac Pro

[NewObject23]

For the past month or so, I've started to have some really weird problems with my Mac Pro. Applications will suddenly stall out or freeze up (endless rainbow wheel), and Force Quit won't work to quit them. It happens most often with iTunes and Finder, but it's also happened with Firefox once or twice.

The whole system doesn't freeze or stall - I can generally still use another application (i.e. if iTunes stalls and won't quit, I can still continue to use Firefox, etc.), but generally if I leave it this way too long another application with eventually freeze, forcing me to shut down by holding down the power button (Shut Down won't work in these cases).

Occasionally when this happens, I have left my computer alone, and sometimes it unfreezes or unstalls by itself, but this is usually hours later, and sometimes it doesn't do this even after hours of waiting.

I ran a hardware test thinking that faulty RAM might be the issue, but the hardware test said everything was OK. I don't know if I should believe that or not. I've tried repairing permissions and verifying all disks, internal and external, and everything checked out OK.

What is going on here? Why do things keep freezing/stalling and forcing reboots?

Here is what I've got:

2x2.8GHz Quad-Core Intel Xeon
2GB 800MHz DDR2 FB-DIMM
Running Mac OS X 10.5.8

I have really normal stuff installed - MS Office, Photoshop, Ableton, etc. No really weird third-party applications other than some really simple stuff. I'm not the type to overwhelm my computer with a bunch of crap.

Any ideas what's going on here or how to troubleshoot this?

Thanks in advance for any ideas...

[Mark Booth]

Try pulling out your memory riser cards (with Mac Pro off, obviously) and reseating all of the memory before reinstalling the riser cards.

Mark

[NewObject23]

I opened up the case, removed both memory cards, removed both memory modules, reseated them carefully, did a quick dusting of the area, and closed it all back up.

Long story short: the problem is still happening. Could it be that one or the other RAM modules are defective?

Thanks for your help.

[BEM]

I seem to be having the same problem since a few weeks.
It started after I installed Snow Leopard and I assumed that was the problem, but from this thread it seems it's not SL specific.

There's nothing showing up in the console either from what I can see, hardware tests are fine too.

In another thread it was recommended to repair permissions, which I've done but the problem persists.

Could it be the HD failing SMART tests? Which I've run too and no problem reported.

2x2.8GHz Quad-Core Intel Xeon
4GB 800MHz DDR2 FB-DIMM

[Aravintht]

I had exactly the same problem as you!

when i installed snow leopard, my energy saver settings were changed.

the mac kept putting all my hard drives to sleep.

which is why when i searched for a song in iTunes, the search was instant as the database file is stored on Macintosh HD, but all my music is stored on my 3rd drive. So the 3rd driver had to spin up and as itunes couldn't find the file immediately, it got confused and froze.

in firefox, when saving a file or acessing a website that wanted to read cookies, same thing happened.

try it - turn off the option to put hardisks to sleep automatically!

let me know if it works!

[j2048b]

any one recently add a ups by chance? i noticed mine doing this last night after i installed my apc ups, ?

any corellations?