You didn’t say whether pload was your program or something else. The last part “too many files open” looks like an errno string.
I’d have to guess (only a guess) that you’ve run out of fd’s. Pretty difficult under QNX 6, but in a loop quite possible. Accessing procnto, hmmmm. I think procnto mediates the allocation of fd’s in general, but in particular it deals with shared memory.
If the program doesn’t abort when this happens you could try “pidin fds”. If your process is running out of fd’s, you will get a very very long list.
BTW, at this point 6.3.0 is pretty ancient. I upgraded from it a number of few years ago because the SCSI driver was unstable under multi-processors, a problem that went away with 6.3.2.