Wizard buttons do not work when you "click" on them under Unbuntu 9.10 Karmic Koala! You can navigate to them with the keyboard and use the space bar to perform a "click".
Some research shows this is an Eclipse Bug with respect to the latest GTK library (they did not migrate SWT away from some deprecated API and the rug was pulled out from under the SWT team....)
There was a workaround (adding an environmental variable to our udig.sh script which worked for linux 32 - but not for linux64.
The only solution is to migrate to Eclipse 3.5.2 when it is available.
Here is the release schedule for eclipse: