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.

Thanks Elliot! That is very helpful!
This needs to be published for sure. I screwed around with it for an hour, then googled it…found your post, and thanks!
Thanks for this blog post. only place I figured out the issues I encountered. Should be stated in the manual.
Thanks for this post! It helps me a lot with the SVN and SSH
Thank you so much….great advise