pins 2-13 don't work as input, only as output

I am new to Arduinos, and my new Diecimila's pins seem funny. I can only use digital pins 0 and 1 as input, pins 2-13 do not work as inputs. When I run the "button" example sketch, the output pin will respond to input on pins 0 and 1, but not on any other pin. Sometimes it will respond for one moment, and then stop working. Sometimes, jiggling the USB cord, which I am using for power, will cause the LED on the output pin (I usually use 13) to flicker. It gets weirder though. When I move my finger near the active digital input pin that I am running the the program with, the LED will turn on as the program dictates. When I move my finger away, the LED turns off. I am grounded. Sometimes the LED stays on for awhile after I move my finger away, sometimes it turns off as soon as I move my finger away. Sometimes it just turns itself on and off without any input. Regardless, only pins 0 and 1 can reliably work as digital inputs, and they work very well. I don't think I did anything that could have fried pins 2-13, and they all still work great as outputs. They just no longer work as inputs. Is there anything I can do or should I send this Arduino back?

Thanks!

This sounds like floating inputs / outputs.

Are you using pull up or pull down resistors wirth your buttons or switches ?

I was using the push button on an Arduino shield. I know the shield is working fine, since it worked on another Arduino.