Your problem is that the version of the SVN client got upgraded locally; whereas your local working copy (and the server) didn't change! Now the new client is unable to work with the existing working copy.
Now you have three choices:
- You can try to get your new SVN client to accept the existing working copy
- You downgrade your local SVN client to the previous version
- You throw your existing repositories away and start with fresh checkouts
For option 1, you might look here or there.
For option 2, this might help.
Option 3; I guess, is the one-line-no-brainer which maybe costs you download time, but should come with the least amount of "you spending your time" debugging this (unless you got a ton of uncommitted changes sitting in your current repositories). But of course, you would first try to create a new checkout with the new client, before throwing the old directory away.