"An error has occurred while trying to start the selected program"

I am at a Fed EX store using a 25 cents a minute computer. I put in the U3 and all the programs work here except Mozilla Thunderbird and Mozilla Firefox browser. Nothing happens except this message comes up in a window with a big red circle and a white "X" and the top of the window says, "U3 Launch Pad." The message is: ""An error has occurred while trying to start the selected program" I uninstalled and re-downloaded the programs, but get the same message. Other email programs work like: "Reach-a-Mail" (a U3 program), but I want Thunderbird!