EDIT: Should now work after form submissions.

Old Answer: Note this only happens for pages with POST data, and automatically refreshing such pages is potentially dangerous! Firefox is showing you that warning for a good reason. If the addon is otherwise working as expected, a 1-star rating (as opposed to subtracting 1 or 2 stars for a missing feature) is a bit unfair just for not letting you shoot yourself in the foot. I'll see if I can implement support for this though, and let you know here in the comments.