Issues with Snow Leopard Software Update

I've run into issues running software update on two separate computers trying to run SL Software update, and am wondering if anyone here has any thoughts.

I'm installing SL from retail DVDs purchased directly from Apple-one is SL Client and the other is SL server. Both are shipped as 10.6.3 on the DVD.

This first came up installing SL Server on a Core Duo Mini. I did a clean install on a clean partition, then hit software update(after doing the regular server set-up). The update downloaded from Apple just fine, and I was given the message that I needed to restart. I hit restart, and the computer stalled at a blank desktop. There was no progress bar or anything else. I've done my fair share of software updates on every version of OS X from 10.2 to 10.10, and I'd never seen anything like this at least for an extended period of time. I left the computer running overnight, and it still was stuck here. I shut down the computer via the power button and it started up fine.

I tried again, and it attempted to install the updates but stalled at the same place. After a few cycles of this I finally gave up.

Earlier this evening, I did a clean install of SL Client(again, 10.6.3 as per the markings on the DVD) on a Macbook Pro with a brand new, blank hard drive. I hit software update. Again, it download the updates but I'm stuck at the blank desktop after hitting "restart". I've been sitting here for an hour looking at it. The cursor is still "alive" but it's not doing anything beyond that.

I have this computer set up to dual boot SL and Mavericks, and I was able to install the Mavericks updates just fine.

Any thoughts on what could be going on here?

Thanks-I did that(I had to hunt down the server combo update as well). Interestingly enough, on my Macbook Pro, after first applying the update it would kick me back out to the login screen. I did a clean install, then ran the combo update again and it worked.

I used software update to do the rest of the updates, but selected and did them one by one hoping I could find the problematic one. They actually all updated fine when I installed individually.

These are probably going to be the only computers I install SL on(although I may put client on the Mini), and with no further updates likely coming I suppose I can deal with that.