2009 MacBook Pro 13" Trackpad malfunctions with new charger

Hey everyone,

I just bought a new charger on Amazon for my 2009 MacBook Pro 13". For some reason, the trackpad functions very poorly, making the computer all but unusable, when the new charger is plugged in. I checked before I bought it and this computer is rated for a 60W MagSafe power adapter, which is exactly what I bought. But for some reason the trackpad doesn't function when the computer is plugged in. When it's not plugged in, the trackpad works just fine. Has anyone ever experienced this? I don't see how the charger would mess up the trackpad. Can this be fixed or do I just need to get a new charger?