Me and my GF just booted up the game today and we both got this error. Admin mode gets around it, but it's really weird that we've been playing this game for months with no problem, then POW, problems. Super strange.
Edit: also, in reply to Xeno, I tried setting up an exception and it didn't work for me, but you can always right-click on starsector.exe, click Properties, select the Compatibility tab, and select "Run this program as an administrator" and save. Then you don't have to intentionally run it as an admin every time.
(It seems that adding an exception only prevents the excepted item from being included in virus scans and such, not necessarily granting it any privileges.)