I do not used ajax mode - it's forbidden. And in server mode looks ok.
But in client mode there is next problem (checked ff and ie)
see screent "initial load" - that what I see on initial rendering
see screen "moved to show all" - I moved it slightly to left and top(without additional loadding occurs). So seems map actually loaded but for incorrect viewport.
see screen "after moval" - I moved it to display zone which was not pre-loaded. that what you see again after loading.