Orbital Decay/Terrible Frame Rate

[overkill13]

I have been seeing constant orbital decay in both 1.7.2 and 1.7.3.  It seems as if physics/air resistance continues to be calculated above 70km around Kerbin for the active vessel.  I don't see this around the Mun or Minmus.

Furthermore after upgrading to 1.7.3, I am seeing terrible slow down in game play, particularly with space planes in orbit, as if the physics calculations are bogging down the game.  Only seems to happen with craft with wings  These are craft I have used in previous versions without issue.  Each time I recreated them from scratch.  I upgraded from 1.7.2 before accessing the plane parts in this particular career mode. 

I just attempted to launch a single piece space station consisting primarily of 2.5m fuel tanks, hitchhiker, science lab with some radial bits all contained within a fairing, which had intermittent normal speed and very low frame rates and returning to normal play at roughly 20 second intervals.  Once finally in orbit I had no problems.  Launching virtually the same space station in this career when I was still using version 1.7.2 did not suffer from any of these frame rate issues.

Removing a ton of mods did not solve these issues.  Completely reinstalling 1.7.3 and the Making History and Breaking Ground DLCs also did not solve the issue even on a stock game.

I found my old 1.7.2 installer I reinstalled the game and found the orbital decay is the same, but a hastily put together space plane does not have the same framerate issues.  I am unable to confirm with the exact same craft, in the same save for the other complaints as the game is blocking all craft and save files from 1.7.3.

Is there any known problem that would cause these issues?

Is there a way to recover my saves and craft files for use in 1.7.2 again?