Looks like xubuntu's gui is a bit oversimplified, and is missing that checkbox. You can use chmod +x from the commandline. See http://forums.linuxmint.com/viewtopic.php?f=110&t=54204&start=0 for someone that had the same problem.
Looks like xubuntu's gui is a bit oversimplified, and is missing that checkbox. You can use chmod +x from the commandline. See http://forums.linuxmint.com/viewtopic.php?f=110&t=54204&start=0 for someone that had the same problem.