To connect to Subversion repository via svn+ssh protocol you should explicitly provide SSH tunnel settings in the Subversion configuration file. Please add the following line to the [tunnels] section of the Subversion configuration file %APPDATA%\Subversion\config:
[tunnels]
ssh = "C:/Program Files/TortoiseSVN/bin/TortoisePlink.exe"
ssh = "C:/Program Files/TortoiseSVN/bin/TortoisePlink.exe"