Answer
The program is either unable to compute the call to check your disk space or:
You have multiple disk drives and specified a drive that is different than the one you are seeing with 250 GB.
It could also be that your RAM is insufficient for running this game.
Most likely it is your RAM specifications because of the game running slow.
The game updated its debug logs or error lists and pulled from that list when it was opened and displayed that error message.
Explanation: