I've trawled through the previous postings on this but they all seem to relate to SVN+SSH, we use a basic SVN server locally.
I've just installed 11.04 on my main development box, side-by-side with my previous 10.04 install, and gone to start checking out the source and everything returns 'Network connection closed unexpectedly'. Forcing a username & password doesn't help, I've turned on debug in a local svn config file and still no real useful information.
EDIT: Just to add Subversion works, an svn co on the Google Breakpad source is fine (as are other repos), but internally it seems to throw it. Other machines are connected to the server fine, if I reboot this specific machine into 10.04 it's fine as well.
EDIT 2: And now it doesn't work on the machine when I reboot into 10.04. Machine is connecting fine to the outside world, and also fine to the server it's on.
telnet <server> 3690. Also do you see the svn server listen on a public address when you runnetstat -tlpnon the server?