When using Mac OS X, you will encounter issues when using SVNKit as the SVN interface from within Eclipse when your SVN password changes. To alleviate the issue, you should install the JavaHL Subversion client and leverage this SVN interface from within Eclipse instead. You may need admin privileges on your computer to perform these steps.
To download the client for your version of Mac OS X, navigate to http://www.open.collab.net/downloads/community and select the appropriate Subversion binary (registration required). Once you install the DMG, you need to update your SVN interface in Eclipse by going to your preferences, then select Team->SVN and change your SVN interface to leverage the newly installed JavaHL client. This should alleviate SVN password caching issues from within Eclipse.
For further information on JavaHL, please see http://subclipse.tigris.org/wiki/JavaHL.
That is how you solve SVN password caching issues with SVNKit and Eclipse on Mac OS X