I've just tested with 5000 dropdownlist, each with 40 items, without a problem.

Also I doubt if controlP5's push-popMatrix methods are recursive, which is what your error hints at.

See: http://wiki.processing.org/w/Matrix_stack

Are you using popMatrix in YOUR code somewere? And are you using it recursively?

However if there is indeed some popMatrix missing somewhere, then a workaround may be to just add popMatrix at the end of your draw() loop (and manually use controlP5.draw() before that).

Thank you for your answer amnon.

If you haven't already done this, it may also help to update to the latest version of the library. Perhaps some errors have already been resolved.

Otherwise it would be helpful to track down the error to a specific controller or a certain number of controllers or something. Some kind of reproducible example error (indeed we don't need your whole code). Because as said, I wasn't able to reproduce the error with controlP5 0.7.5.