I have just experienced this error which I traced to a recent server upgrade and a svnadmin dump/load cycle. The problem was that I had set up the repository in a different directory to the one it was created in.
On the old machine, I was using inetd.conf to run svnserve:
svnserve -r /var/svn/main
and the repository was in /var/svn/main
However on the new machine I had inetd.conf pointing to /var/svn:
svnserve -r /var/svn
I already had a checkout from the old server, so when I tried to commit the destination path didn't exist because I'd accidentally added another component to the URL, so svn://host/source/trunk became svn://host/main/source/trunk.
I could have fixed it by moving the directories around, but I chose instead to rewrite the URL of the working copy using svn switch --relocate.
Note: a quick diagnostic to see whether this is the problem is to change to a directory in your working copy, type svn info to get the repository URL and then type svn ls <myUrl>. If this gives a No repository found error then you know this is the cause.