How did you get the 5.1.5 update to install? I launched SoftwareUpdate using
arch -arch i386 /System/Library/CoreServices/Software\ Update.app/Contents/MacOS/Software\ Update in order to get Software Update to start.
It went through all the motions of installing the Xserve LOM Firmware Update 1.2 and Safari 5.1.5 and rebooted my server ... but the problem with Software Update crashing is still there and I still have Safari version 5.1.4.
I have 2 xserves which came with 10.6.3, which I applied all software updates EXCEPT safari 5.1.4, and they were working just fine -- software update launched and ran with no problems. Installed safari 5.1.5, and they still both just fine. On the other hand, a machine with the 5.1.4 update installed upon it, followed by the 5.1.5 update will still be broken -- whatever 5.1.4 does to break Software Update is not fixed by 5.1.5, but 5.1.5 doesn't break it, either.
@Cathy - my experience differs from yours.
on my first server, after installing the Safari 5.1.4 update, my Software Update application and command line refused to function properly, crashing, etc., as described in this thread.
I used Peter's method to change the gui application to launch Software Update in 32-bit mode, and it performed normally after that.
Today, I used Software Update running in 32-bit mode to install the Safari 5.1.5 update. After the reboot, verified that the current version of Safari was indeed 5.1.5. I then unchecked the "Open in 32-bit mode" checkbox in the Software Update Info panel. Software Update ran normally in 64-bit mode, and I used it in this mode to install the next two updates (Java Update 7 & iTunes 10.6.1).
so, for me, it appears that the Safari 5.1.5 update did indeed fix the problem with using Software Update application. I'll leave it in 64-bit mode and see what happens going forward.
note - @RobJensonCHS - I've seen Safari updates over the past year or so run, but after the Safari update ran (via Software Update application), my version of Safari had not changed. Typically a second round of running Software Update resulted in an updated copy of Safari, although at least once I had to run it 3 times!
I ran across this today as well, on our xServe (xServe2,1). It took me a lot of work, but I tracked it down to the Xserve LOM Firmware Update-1.2 update. The installer from the web also crashed. Once I disabled that in our SUS, Software Update worked, and once I upgraded to Safari 5.15, I could renable the LOM update, and Software Update wouldn't crash. I could also run the installer (and it told me the server didn't need the update).