I don't think that if it was an Ai or AiS lens would make any difference. It is the difference between the acceptance angles of the different lenses where a wide lens may take in more high or low light areas than a shorter focal length lens which will produce the different results. This is one of the main drawbacks of an averaging metering system
The op didn't say what kind of lens it was. It could be pre AI lens. In such case it could be the cause of the problem.