This post started off as a cry for help, but I figured it out and am leaving some information for someone else who might have the same problem.
If you're running Debian Squeeze and install scummvm from the standard repository, you'll most likely get version 1.1.1. This version has some sort of bug that prevents you from opening the safe. Update to the latest version (at least 1.4.1) and things should be good.
LGOP2 opening the safe (debian squeeze)
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