I just wasted an hour on this, so I hope that explaining the solution here will help someone. If you’re using TortoiseSVN and PuTTY, perhaps using a private key created with PuTTYgen (like me), then this probably applies to you. I’m using Windows XP Pro, but Home is probably the same. I didn’t have this problem before because I just used cygwin’s ssh.exe which worked fine.
PuTTY Internal Error
Invalid Port Number
For TortoiseSVN’s SSH cilent, leave the box blank. Do not choose putty.exe, that doesn’t work. Blank is fine, TortoisePlink is fine. Otherwise you see the error above. When you enter the URL to the repository, use the PuTTY saved session name instead of the server name. For example, if your session is MyConnection, use MyConnection for the server instead of, for example, svn.osafoundation.org.

Thank you! Worked for me, too.
At the moment i am still using password authentification. For all those who are doing the same led me add, that I needed to insert my Password 3 times in a row. This distracted me quite a while.
Thank you very much!
thanks. that did it.
Thanks! It did help
Thank you soooooo much… 2 days I’m getting crazy… Great advise…