Another user encountered this recently, and, using the Fortran debug
utility, was able to locate the instruction causing the error:
INFNTY=SQRT(LARGET)
in NONMEM's INITL subroutine.
It turned out that he was using the (default) IEEE constants in BLKDAT
rather than the INTEL constants, which are the correct ones for the IBM
PC. Once BLKDAT was modified as described in NONMEM Users Guide III,
p. 16-17, the problem disappeared.
See also
NONMEM Level 2.1 Update