[morris]

Right - this is what I'm about to try to implement (and I think I'd trash the entire queue if a response isn't returned within some timeout limit and display a subsequent error message). I don't know if this is the best practice though and as this seems like a pretty generic AJAX problem, it feels like there should be a pretty generic solution...

[jey]

I doubt most AJAX applications are that reliant on request/response ordering. However, a priority queue is the generic solution. :-)