Can I revert a full "software update"?
 

I feel like a hack mechanic who has completely disassembled an engine, put things back together, and now has a bucket of extra parts. Things are no longer running correctly, and I'm having trouble getting things back to their original state.

I am running Fedora 12, on a Mac Pro with an ATI GPU.

ATI drivers are particularly problematic on Fedora 12, but were working well enough with my 3D application as installed "out of the box".

In an attempt to fix a GL problem, I installed "mesa-dri-drivers-experimental" which completely broke my application. After uninstalling, my application still seg faults so I'm convinced that something was left in an altered state. Digging deeper, I tried updating graphics drivers with no luck.

After being unable to get to my previous state, I allowed Fedora 12 to do its full "software update" in the hopes that various driver issues would be repaired. However, when I boot from the new Grub entry and new kernel, X now fails completely, leaving me with a blank screen. Using the old Grub entry, I can still boot to the older kernel and at least get to my Gnome desktop. Graphics drivers are still misbehaving, and my application continues to crash.

I would ideally like to restore the drivers to the "out-of-the-box" versions. Am I better off reinstalling Fedora from scratch, or is there an easy way to fully revert the changes that have been made in the last 24 hours?

Please let me know which log files might help reveal more detail.

(Also, I'm curious where in the file system changes are stored. How is it that I can boot an old kernel, and have a fully functioning X desktop, but the new kernel gives me blank screens? Is all this information contained within the initrafms image?)

Thanks in advance.

As I am digging deeper, I have just discovered the yum history command. It looks like I might be able to revert various transactions this way. Does anyone have any experience with this?