Have you tried to change the walltime option to the number of seconds, e.g.
#PBS -l walltime=36000
for 10 hours. Anyway, the output and error files should be generated vene if they are empty (this is the normal behaviour). Try to look if they was undelivered: if this is the case you can find them under /var/lib/torque/undelivered or /var/spool/torque/undelivered (again the default, unless otherwise ordered by the sys admin).