Cannot launch applications sometimes

Question

Hi there,
I've got a knarly issue here. After a certain period of time (a couple of days for instance given that I leave the machine switched on) I cannot log into my computer via the screen saver password prompt (I just get the spinning ball, no login dialog displays). Additonally, at this time, I cannot ssh to the machine (whereupon I normally can). Finally, I have been doing something on the machine (using various applications) and then find myself unable to launch any other application via the dock (bouncing icon eventually times out). The latter problem has happened twice. In this instance I can still activate applications that are already running (they come to the front etc.). Additionally logging out in this instance is a problem and I have to force-quit things to get through the logout (including the Finder). Finally when it gets to actually logging out, I don't get the dialog to login again (just the clock style progress indicator with the bars which goes on forever).
Very mysterious. I've a suspicion that the above problems are related.
I have done a couple of things to this machine that may be relevant: increased the RAM; and (ii) updated the Pioneer DVR-110D firmware (this was a third party drive that I bought given that the original drive stopped working).
I have run memtest on the memory with several passes. Everything reports ok. I realise that memtest won't necessarily report all faults, but I know that if it does report a fault, there's definitely a fault. I want to get my hands on the Apple Hardware Profiler to do another test - anyone know how to get it?
Most importantly can anyone explain any of the symptoms I'm seeing? The machine is obviously still alive given the spinning ball when trying to wake up from sleep in the screen saver, and activation of existing application.
Any clues and diagnostic ideas are greatly appreciated.
Cheers,
-C

Answer 1

re: SSH. I presume you've enabled Remote Login on the
affected Mac? Remote Login has to be enabled before
the problem occurs if you are to SSH into a
frozen/hung Mac. However, depending on the problem,
the affected Mac may be so frozen or hung that you
simply can't get in via SSH.
I can normally log on to the machine using SSH. In fact, at one time, I established an SSH connection and then the problem occurred subsequently. My SSH connection, having already been established, allowed me to look around the machine.
In lieu of the AHT, and as noted in my AHT FAQ, you
can use Micromat
TechTool Pro 4 for hardware testing. You want to
use version 4.0.4 or later with Tiger, but it is best
to use the latest version, which is 4.1.2. You'll
want the CD so you can boot from it to run the
hardware tests.
I will look into this software now.
Another small update: given that the machine went weird again yesterday I managed to mount a volume via AppleShare and have a look in /var/logs. However I didn't see anything really out of the ordinary. Given that these logs get archived on reboot, any ideas on something that I might look for?
Once again the symptoms are that: I cannot su to any other account (whereas I normally can); and (ii) I cannot launch applications (also whereas I normally can of course). Apps are launched via the Finder Dock. I'm suspection that (ii) is caused by . The fact that I cannot su to any other user is most weird.
The machine is now running without the non-Apple memory, Activity Monitor is running and I've disabled passwords being required to wake the computer up. Thus if it does go down again I should be able to do some more diagnosis.