If you are using Tortoise SVN and Zend Studio on Windows machine you may encounter this error message:
"svn: This client is too old"

Zend Studio ships with a cvs and svn clients which allows you to commit directly from the editor.
However, when you start using TortoiseSVN and perform an update to a checked out codeĀ  TortoiseSVN

will update the format of .svn files.

That's why you see "svn: This client is too old to work with working copy".

Solution:

Download and Install CollabNet Subversion Command-Line Client for Windows

Tell Zend Studio that you want to use a different svn binary.

Go to Tools -> Preferences -> Source Control

[General Settings]

change old:
C:Program FilesZendZendStudio-5.5.1binSourceControlsvnsvn.exe

to:
C:Program FilesCollabNet Subversionsvn.exe
Note:

Please note that you need the SVN client, not the Server ;)
Slavi