I've been playing with perl/Tk, and had several problems with images.
I'm thinking that its possible that you have found a bug in the current version. You are up to date with the latest and greatest in CPAN? Have you a bit of driver code that benchmarks your memory usage yet? As in, load 1, measure memory, destroy, load next, etc?
Also, I'd be interested to see what happened if you don't scale your images.
HTH
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Jay "Yohimbe" Thorne, alpha geek for UserFriendly