My first thought was plantar fasciitis too.  Its common in runners and a look on somewhere like RunnersWorld will tell you lots about it.  I can get pain where you mention if I have neglected stretching my calves and achilles for a bit after both cycling and running, in fact it feels a little bit tight now after last nights ride.  I have pretty tight calves normally so need to keep on top of it.  Do you stretch at all ?

Sorry just read that you stretch and it goes away, same with me really so you may just have to make a big effort with stretching.  Plantar fasciitis is a bit  more serious I think, you don't want it!

I've had the EXACT same problem all last year just as you described Yolinda - pain on the back heel - getting out of bed first thing was a painful experience, tip toeing around the house trying not to put my heel down!

Basically too much biking not enough stretching - simple as that. I saw a private doctor and physio and it was a long healing process but trust me those calves need stretching out after every ride and hamstrings too. It builds up and before you know it you'll have a serious problem. stretch stretch stretch!