Were you shooting with flash and using the prism meter? I think that might be hard to do and keep everything tight.

Are the batteries in the meter fresh? You may want to borrow a friend's meter first to make sure. Compare readings on that or you could also try metering the same scene with another known camera to see what that says.

One other tip with those prism meters, you should make sure to focus first before you meter. The extension of the lens does affect the metering.

Like CGW, the Sekonic L-308s is a nice little FLASH-capable meter. But it's about $200 new.

Good luck!