The Url Master module is compatible with the NB Store module.

The NB Store module uses a querystring to show the store skin, and that path includes the /desktopModules/ folder.

The standard 'doNotRewriteRegex' value in the Advanced Regex Filters section on the Friendly Url Settings page contains a pattern preventing rewrites on the /DesktopModules folder.

You need to update the 'doNotRewriteRegex' value to this:

(?<!skinsrc\=)/DesktopModules/|/Providers/

The change prevents matching the /desktopModules/ path if there is a skinsrc= preceding it.