I don't think that the svn.exe executable is present in the mentioned folder. If you have a Subversion client installed on the Collaborator Server machine, try specifying a fully qualified file name of the svn.exe executable. It should be present somewhere in the installation folder. For example, I have the native client installed on my machine and the fully qualified file name is:
Just came across this as I finished troubleshooting on a subordinates computer and checking to see if any documentation already exists.
The solution, if using TortoiseSVN, is to enable installation of the "Command Line" interface with Tortoise. The package within our corporate IT sites had defaulted this option to "no". "svn.exe" will only install as part of the "Command Line" options in Tortoise. The current online installer from the Tortoise web site has all options enabled.