Carharrt:
Remember to clear out the contents of your 2D patch file after a failed patch. That can stop a patch from happening, on occasion. But, before you do, look through the patch.log file and see where it failed. Sometimes you can copy the damaged file over from another install (of the patch, or from the patch that was being overwritten - either will work) to get the patch to restart.
This is one of the reasons why I keep UO installed and patched up on multiple machines, even though I play 95% of the time on one of them. Between the two machines, I've had this kind of thing happen at least 3 times in the last 2 years, but by replacing the broken file on 1 machine from the other, I was able to avoid a reinstall. On 1 machine (or as a further backup) I typically copy the entire folder from Program Files as a last ditch save method (at worst, I just copy it back over and reinstall from there, but never had to do that yet).