The problem is probably that your working copy has meta-data format (1.7) that your actual SVNKit cannot read.
Apparently you have checked out the working copy outside from eclipse with a newer version of an svn client.
The error mesage says it all, to resolv your problmem you could try to update the subversion plug-in of your eclipse. You can find the update site for the version you need in this page.
Hope it Helps.