I have had a similar experience. Using the [ or ] keys to switch cause my station that I am assembling to go boom. If I go out to the tracking station and come back I don't have an issue. I did some digging on the forums about it and it appears it is an issue that started in 19 or 20 and supposedly was fixed in 20.1. http://forum.kerbalspaceprogram.com/showthread.php/30923-Ship-explode-instantenously/page3 is the support thread. It appeared related to some docked parts not being attached correctly in the saved files so when they were switched to they were in orbit and collided with the rest of the ship? If other folks are still hitting this I would say we try and get the data Squad needs to debug it and we necro that thread.