Another solution, albeit one that involves a bit more work, is to switch to the Dvorak keyboard layout. 'e' and 'r' are no where near each other; in fact, they're typed by different hands. Plus, your wrists and fingers will thank you.

Please note that this post is mostly in jest. I realize that learning a new keyboard layout merely to prevent goofing up the 'e' and 'r' keys would be a bit silly. However, I do find typing much nicer with Dvorak than I did with Qwerty. Just ask Juerd about it:)