Hey Jamie,
When a user first installs the system, we have Subversion configuration disabled, since so few users need/want it, and it just adds more options to an already overwhelming set of options...but for the users that do want it, they get a less than helpful error when browsing to the module:
You do not have access to any Virtualmin servers
Which leads them to think something other than "Subversion hasn't been enabled". Maybe the error for this particular case should be more along the lines of:
Subversion management has not been enabled in the Virtualmin Plugin Module page. Click here to enable it.
And then, once that's done...The above error, which still appears, makes a bit more sense, though it's probably still not as informative as:
Subversion management has been enabled, but no virtual servers have been granted Subversion privileges.