I accidentally flipped the SD card to "lock" and inserted it into my computer. When "Save Toolpaths To Disk" and selecting E:, the software says "Unable to export to selected location." (as i would expect).
Then I eject the card, and flip the switch, and reinsert the card, and "Save Toolpaths To Disk." and it still gives me the same error. The only way to get rid of the error is to exit the program and relaunch SImplify3d.
Small bug.