Been helping a client whose Drupal 5 site is not working properly with respect to Ubercart (possibly other site issues?). I have updated the site from Drupal 5.15 to 5.22, plus all contrib mods, on another (development) server - separate from active live site. However, I have not used Ubercart, so I have gone as far as I am comfortable going. Client wants to change hosts, so your work would be done on the development server (new host - HostGator), and DNS changed over once everything is working properly.
The ecommerce aspect has been down for weeks/months now, so he is anxious to have it working.
If interested, contact Charlie at cruise @ groupcruising . com (no spaces in email, of course).