I have exactly the same issue with you. I have TortoiseSVN installed on my windows, I have also eclipse installed, in the eclipse, I have the subclipse 1.4 installed.
here is the issue I have proxy settings, I can open the repo through web browser, for some reason, I cannot open a repo through svn. I tried to change the proxy following the link below Eclipse Kepler not connecting to internet via proxy. It doesn't work.
Finally I found out a solution
You have to change the proxy setting in TortoiseSVN. After I enable the proxy setting the same with my browser. The issue is gone.
here is the link of how to enable proxy setting in TortoiseSVN https://tortoisesvn.net/docs/release/TortoiseSVN_en/tsvn-dug-settings.html Seach "Network Settings" on the page above