Chain malfunctioning?
 

I bought a Raleigh Grand Prix. The bike is great but the chain sometimes comes off when I am really pushing the pedals hard. I wonder if it is because the rear sprocket has 10 gears and maybe the chain gets pulled to the path of least resistance. Has anyone ever had a problem like this.

The problem made itself visible on the first ride and continued to persist after my first tune-up. It is very aggravating to be in a good rythm and then have your chain pop off. I told my bike shop about the problem and they said they couldn't find any problems. The store owner said he even took it for a ride himself. I am lost and don't know where to go.

I would take it back once more. Remember to talk to the people who are actually good at working on bikes in the service department, some shop owners are good business people, but don't know squat about the workings of an intricate machine. If they don't get it right, take it to some other shops around (if possible). 10 spd is a little finnicky, but should not jump off under normal riding.

Where is it coming off at? Chain rings or cassette? What gears are you using when it comes off.

It is definitely coming off at the chain rings when I am in my highest gears.