I had this problem, too. I made some mistakes loading my dumpfile, and recreated the repo with "svnadmin create". Bad idea.
The Panel creates the repository with "dhapache" as the owner, and the reponame.access and reponame.passwd files with "dhapache" as the group. Trying to create your own repo with "svnadmin create" is futile because you don't have authorization to change those ownerships and group memberships (and you're not a sudoer).
Also: don't overwrite your reponame.access and reponame.passwd files with 'echo >' (e.g. if you're trying to use MD5 passwords). Use an editor and paste in the new data. Overwriting will cause the files to have your user's group instead of "dhapache". If your repository is relatively mature when you make this mistake, and you have no backup, you could be toast.