The size of the system that can be created using these scripts depends on the size parameter used when CHARMM was installed at your site. To resolve this you have to re-install CHARMM using eg LARGE or XXLARGE. Note that even if the final number of atoms/residues could be handled by your present CHARMM version, the scripts may still fail at an intermediate stage when water molecules are being added. This issue has been discussed before.
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Lennart Nilsson
Karolinska Institutet
Stockholm, Sweden