Another Runtime error...

The following information is required to get an answer:
Get this information from the PHP diagnostic (in the configuration wizard).
Gallery URL (optional but very useful):
Gallery version:1.5.2 pl2
Apache version:
PHP version (don't just say PHP 4, please):
Graphics Toolkit:
Operating system:
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It seems there have been quite a few runtime errors I've found. See attached. How do I fix this one?