VueScan is a very popular non-FLOSS, but cheap professional scanning software. Another time I will write a review. For now I want to focus on getting it to run on the newest Ubuntu version 11.04 Natty Narwhal.
Starting VueScan by a double-click seems to do nothing on 11.04 while on 10.10 it worked perfectly. Actually what happens is that there is a bug in compiz that has the effect to not show VueScans windows, when actually it already started.
For now there is no fix and you have to live with the workaround found on ubuntuusers.de to logout of your current session that I assume is a Unity-based session. Upon a new login choose “Ubuntu Classic – no effects” and VueScan will start normally.