Steps to reproduce.
1. File -> Clone / New...
2. Enter the URL of a subversion repository

• I've tried a WebDAV + Apache Subversion system and a VisualSVN Server

3. Enter a Username and Password when prompted
4. SourceTree reports: "This is not a valid source path / URL"
5. Clicking Details... displays this error:
Can't open perl script "C:\Program": No such file or directory
fatal: respository 'http://<snip>/svn/<snip>' not found.