are you by any chance on windows ? I'm testing my app on that and for sure something is going on like you described.
I have a page full of loaded ajax components that on linux load semi-concurrently while on windows they are fully serialized (i.e. the browser fires ajax "all in one time" and on linux several of them are loaded at once while on windows the "next request" is fullfilled only if the "previous" one is completed).
