Check the thread called ;
How many bolts hold your axels on?
I posted there how I fixed the problem.
I hope you can follow it, as it is a little confusing.
If they all slipped, it isn't as bad if only one or two slip, as that places uneven loads on the axles and tires.
As far as I am concerned, it is pathetic how the factory mounts these, and they should be adding the extra bolts as I did.