The wizard buttons in Eclipse 3.5 Galileo do not work with gtk2 2.18. You can get around it by pressing the Enter key, but that’s still a pain.
The solution is to create a file that starts eclipse with GDK_NATIVE_WINDOWS=1
Example, create a file starteclipse with the following contents:
#!/bin/sh
export GDK_NATIVE_WINDOWS=1
/opt/eclipse/eclipse