Conditions for loading errors?

What would cause a loading error (red loading bar/ red loading percentage) to occur when adding in an animation or frames to an animation (i.e. my game loads fine, then I add in an animation and import frames to it and now there is a loading error and it won't load. I should note I can add as many blank frames as possible but adding in any other sort of image in the frames caused a loading error).

EDIT:

It seems to happen when I add in more than 1 non blank frame in certain animations, though since I can't reproduce it consistently, I am hesitant about posting it to a bug report section. Also now it loads but just gives these error messages

http://puu.sh/o33u5/ee7b4f204c.png

http://puu.sh/o33zQ/0236c4595d.png

Update: The error messages were caused by Spriter clashing with the 2 objects in question somehow. If those 2 objects are deleted, the game loads fine. If the objects are there and the Spriter object is deleted, the game loads only when loaded from the layout that the objects were on, and has a loading error on other layouts still so the 2 objects are still troublesome. I have tried remaking the 2 needed objects from scratch. On checking the loading with every change, it errors after adding the frames to animation #10 on the first object and animation #3 on the second (tested separately).

Any ideas?