confused after one night stand

let me start by saying i am happily married and have never even remotely wanted to cheat. when i was younger i had many relationships and only met my husband in my early 30s. we have been married 10 years and have a family and i have a good job and a happy life. all sounds great but i have a real problem. we had a very drunken party with our neighbours recently and during the evening i found myself alone with my neighbours husband. we have always been friendly but nothing more and i have no idea why, but i kissed him. suddenly we were all over each other and i ended up having sex with him on their bathroom floor. the whole thing only lasted about 20 minutes but was very intense and very exciting. im ashamed to say i acted completely out of character, doing things i normally dont like to do. i had several amazing orgasms (as did he) it was like a switch was turned on in me as we kissed and i became someone esle. the following day we talked and agreed it would never happen again (which it hasnt) and we went back to exactly how we were. we've never mentioned it again and no one found out. my problkem is the strength of feeling i had for him, even though i never had before. sinc ethen we have been alone a couple of times and although nothing has happened i get extemely turned on - one time he brushed past me and i swear i nearly came on the spot. i dont fanatsise about him, in fact my only fantasies are about my husband (i still have a great sex life with him). all this happened a few months ago and the other day i plucked up the courage to talk to my neighbour about it. he admitted it was the same for him - when he's near me he gets extremely aroused, yet mostly never thinks about me and is happy in his marriage (in fact he & his wife are expecting their third child) I don't understand - is it possible for two people to have an attraction like this? is there something wrong with me? I now daren't go around to their house (which we used to do a lot) and people have started to wonder why?