Subversion unable to open an ra_local session

I've setup a Subversion repository on Windows XP at the following URL:

file:///S:/svnrepository/whatever

This is Subversion 1.2.0, I setup the repository as fsfs.

TortoiseSVN works fine, as do the command-line Subversion tools. But IDEA 5 does not, last tried on EAP build 3405. Pretty much regardless of what I try, such as trying to Update a directory, I get this error message:

Error: svn: Unable to open an ra_local session to URL 'file:///S%3A/svnrepository/whatever' svn: No connection protocol implementation for file:///S%3A/svnrepository/whatever

Something about that "%3A" is confusing IDEA, I think. I don't know what is going on. Here is the output from the "svn info" command executed on the command line:

Path: .
URL: file:///S:/svnrepository/whatever
Repository UUID: 8917d379-3fc4-5c44-b50a-3a5b1a9b3d71
Revision: 9
Node Kind: directory
Schedule: normal
Last Changed Author: Eric
Last Changed Rev: 9
Last Changed Date: 2005-07-11 21:38:00 -0500 (Mon, 11 Jul 2005)