I received a 1099-R for monies that I rolled over from one qualified plan to another when I switched jobs. None of this distribution was taxable. I forgot to enter this information on my 1040A and already filed it electronically. Do I need to file a 1040X?

It depends. Generally rollovers are not taxable, unless it wasn't done precisely to the rules. If you did a direct rollover (meaning your old plan transferred your account directly to the new, without ever issuing you a check) then most likely you're OK. But if they issued you a check and you transferred the money to your new account yourself, you have an issue. Take a look at the 1099-R and tell us what it shows for box 2a "Taxable amount," box 4 "Federal income tax withheld," and box 7 "distribution code."