Also take a look at any ulimit settings, or anything else that may limit how much memory is available to a process. Can you see if the new process is actually using more memory or running into other limitations?
I've hijacked a friendly sysadmin bloke - the ulimits are set the same way, there was no other process running on either box during these tests. I've just stumbled into a big problem though - I don't think I'm going to be able to recompile the Perl without major internal wranglings over support on the box. Arrrrrrgh.
'I think the problem lies in the fact that your data
doesn't fit my program'.