As a temporary measure add the following .reg file to give a right-click option to open with UltraEdit. The current version is 12.20c; hopefully this will soon be corrected in a future release.
Windows Registry Editor Version 5.00
[HKEY_CLASSES_ROOT\*\shell\UltraEdit]
@="Edit with UltraEdit"
[HKEY_CLASSES_ROOT\*\shell\UltraEdit\command]
@="\"C:\\Program Files\\UltraEdit\\uedit32\" %1"