Graphical corruption after update from maverick-beta

Hey everyone. I've been using Ubuntu since Dapper, and for the most part it's been great times. My desktop computer is totally solid, even while running the Maverick beta. However, I've run into a large issue trying to get the current Maverick build running on my old laptop. The device in question is a Dell Inspiron 600M (got it from someone who didn't want it anymore). I had it running Lucid with no huge issues, but I wanted to take advantage of the nicer theme and upgrades to the package repos. I wouldn't have bothered this early, but as I said, it's been running nicely on my desktop. As such, I seem to have hit a pretty nasty bug/regression, and I'm wondering if anyone can help out. Here's what I've got:

I installed the beta using the same cd I had made for my desktop. Installation went through without an issue, and I was able to reboot into my new desktop with no problem. However, after running update manager to do a partial upgrade into the current state of Maverick, I'm unable to get the computer to properly boot on restart. After the ubuntu logo shows up, insead of going properly to the login screen I get a strange graphic... basically a wall containing the purple/white-ish hues of the login background, but thinly vertically striped (it would seem, sort of hard to properly explain, as the stripes are the same color). If I blindly hit enter, and enter my password, the screen goes a strange pattern of grey (similar to the toolbars on the desktop). I couldn't get it to properly do anything from here, except that once or twice I was able to ctrl-alt-del and hit enter to shut down (so keyboard input is working). It kinda sounds like part of whatever is on the screen (a toolbar, for example) is being stretched through the whole screen, but it doesn't look like a resolution issue. I tried reinstalling many, many times (very tedious) in different fashions, to try and nail down what might be the culprit...

- I have tried installing to auto-login, which gave me the same basic problem
- I tried running selective upgrades of certain susceptible (to me) assets: from what I'm recalling now, it doesn't seem to be an issue with gdm, plymouth, grub, linux kernel (tried running the originally installed kernel from the grub menu after upgrading, to no avail), or xserver-xorg (some variations of this, but I couldn't tell you which I tried pinning, specifically... so this could still be the problem).

I'm kind of burnt out trying to nail this down, honestly. When I go to run an update, there are almost 400 packages to be updated, and I'm not good enough at this to know what's the most likely suspect. Can anyone help with this? Has anyone experienced this issue? If it really is a problem, can I help fix it before the Maverick final release? I'll do whatever I can, I'm not a coder, but I can follow terminal directions if it'll help. Probably going to be hard to pin down, but I'm hoping to nail this. It must be a semi-recent issue, if it's not just on my end, since the beta cd installs fine. Hope to hear from a friendly genius! Thanks for your time.