Anecdotal, but keep this in mind:

At one time Solaris had a ridiculously (FSVO rediculous) low default for number of file descriptors per process (not per thread; also not to mention I want to say there was a buglet that the stdio library used an unsigned int so even if you raised the resource limit things going through fopen etc would still crap out quickly (again, FSVO quickly; I remember easily hitting it often with mod_perl)).

To debug you might use truss and watch for open(2)-like calls (things like socket(2) as well) and close calls watching that they match up to make sure something's not leaking descriptors. That number 9 * 25 is 225 which is awful close to 254 which was where the stdio problem reared its head.

Update: Reformatted and extended.