I just downloaded and reinstalled tuxguitar-1.5.2-windows-x86-installer.exe (the same version), and rebooted. Unfortunately, it did not start again. I then started the program using "run as administrator" on right click - and it finally did start! The next time it started even if I did not "run as administrator". Not sure if any of this has anything to do with it, but it works for some reason now :)
TuxGuitar 1.5.2 does not run on my WindowsPro Notebook