Thank you for contacting us.
The scrolling using the mouse wheel works fine for me in the working copies list and also in the working copy combo. I tested on a Mac OS X Version 10.4.9 with java version 1.5.
Please give us more details about your system, java version and Syncro SVN Client version.
It now seems to work fine - I did change my Java version from 1.4.2. Changing my Java version seems to fix a few other small UI issues (at least on 10.4.