In my current project we use a Subversion repostitory for our code, acessing it mainly using TortoiseSVN. For each component in the product we are making there is an MSBuild script file for building that component. These build scripts will perform a temporary change on the AssemblyInfo files, a change that is undone in the end of the build by reverting the change in Subversion. Recently that operation started giving an error message for one of the users:

The client is too old to work with working copy '[the path]'. You need to get a newer Subversion client, or to downgrade this working copy.

We found this a bit odd, since all of us where using the same version of Subversion (1.5.1). I posted a question about this at stackoverflow.com today, and (as expected) the answer was more or less immediate. It turns out that TortoiseSVN comes bundled with its own Subversion client, and the developer in question had updated TortoiseSVN to version 1.6, and so his working copy was updated. Everything was fine as long as the Subversion repository was accessed through TortoiseSVN, but when the build scripts used the older version of Subversion, it failed.

The developer uninstalled TortoiseSVN 1.6, reinstalled 1.5 removed his working copy and checked it out from subversion again, and it all worked like a charm.