I can't help, but do indexedDB storage (used for the save-states) isn't Really Huge?, and so used instead of WebStorage because of that? (so, I'm not sure to store it entierly in the webstorage is a good thing to do).
EDIT: Also, I'm guessing you already save to a Save Slot by doing the system Save action, so, It is just nonsense, again, I can be wrong
EDIT2: you can load, not from JSON, but just load, and enter the name of the slot you selected before, don't use webstorage actions At all.Aphrodite2013-05-26 23:46:23
And that is why you shall respect the bug reports guidelines, not only giving a capx is making the bug reproductible in one click in a situation they can work with (less time wasted trying to reproduce vague instructions) but also it helps filtering false positives.
Game design is all about decomposing the core of your game so it becomes simple instructions.