As LanX might have guessed, I maintain a list of nodes related to memory issues: Re: Perl Memory problem ... (Memory Tools References)

From that node, I suggest you start by mulling over each item in the "General Areas to consider when faced with a Memory Leak" section ... while thinking like a detective. :)

The Profiling Memory Usage talk by Perl legend Tim Bunce (featuring his Devel::SizeMe module) is also excellent (it opens with a joke about your "Out of memory!" message I see).