Keyboard spaces twice

I'm not sure if this is an issue with Mac OS or my keyboard (the standard keyboard that came with my Mac Pro): but quite frequently (but not 100% of the time), when I hit the spacebar, two spaces are inserted into whatever I'm typing. I'm pretty I'm not accidentally hitting the spacebar twice, as it happens very frequently no matter how I hit the key. Does this happen to anyone else? Would this be an issue with my keyboard or is there any way to correct it?

Thanks.