@Whiplash
Stonesense doesn't save any state information between times you load up DF, so the time you maximized it and it "flipped out" can't be the root cause.
If it was working properly before this, as your post indicates, then something must have changed to make it not work. Try making a clean install of DF and DFHack in another folder, and see if that's working. If the fresh version doesn't work, then you have a problem with your system - possibly an OS update or driver update broke something; try to make sure your operating system and video drivers are all updated.
If the fresh version DOES work, then it is a problem with DF or DFHack or Stonesense. Try generating a new world and viewing a fort there in Stonesense. If the new fort doesn't load, then it is a Stonesense/DFHack problem, and you should probably just try reinstalling DFHack (or at least replacing stonesense/init.txt and deleting all the log files).
If the new fort DOES load, then it is likely that your current fort just got old enough to fill memory to the point where there's nowhere left for Stonesense to live. You can try viewing the memory footprint of DF (on windows that'll be in the task manager under the memory heading), since when DF swells to around 1.6Gb of memory, Stonesense can't load anymore because there's nowhere to put the images in memory. All you can do in this case is try to trim the largest images (probably the large creature sprites) out of your load order, and optionally try running some of the DFHack stuff to clean stuff out of your map (like cleanspatter and autodump-destroy).
If none of that helps then I dunno.