I had a long, and mysterious, problem where trying to execute SVN commands on a Windows machine over HTTP would execute normally, whereas over HTTPS they would be extremely slow, but only for particular repositories:
svn info http://iaml.svn.sourceforge.net/svnroot/iaml : 14 seconds svn info https://iaml.svn.sourceforge.net/svnroot/iaml : 14 seconds
svn info http://iaml.googlecode.com/svn/trunk : 7 seconds svn info https://iaml.googlecode.com/svn/trunk : 37 seconds
Eventually, a system administrator came to help me solve the problem. Using Process Monitor, we kept a trace of svn.exe and tried to debug how it worked.
It turned out there was a major delay when trying to execute something through cryptnet.dll. After disabling cryptnet.dll (and allowing Windows to complain), the problem vanished.
Some researching indicated this problem had occurred before: cryptnet.dll was timing out because the machine was not connected to the Internet.
We have to use a proxy in order to use the Internet at Massey. I went into my Internet Connection settings for Windows, and saw that the proxy was being resolved to a script, rather than an actual proxy address. I switched it to a proxy manually, and the problem has gone! Hooray!