I cannot find this in docs! Per device limits on number and type of fitFields?

Hi,

I'm hitting some issues where simulator and device are behaving _VERY_ differently!

Although I am running quite close on memory, there is enough to run safely in the simulator and my pristine, perfect, streamlined code runs perfectly in the simulator, every time, for every device I test.

When I put it onto my device however...

It crashes out during initialize() as I generate the fitFields I'm going to need for tracking.  

ERROR: System Error

DETAILS: Failed invoking <symbol>

Moreover, deleting a chunk of display code to free up more memory has absolutely no effect! The line number it fails on is .add() of a createField() and by the time the line fails, it has already run correctly a number of times...

More irritatingly, as far as I am aware, the fit fields it is generating are no more complex or numerous than similar fields created for another data field that runs entirely correctly.

Any pointers, please?

G