Sometimes Magento Community Edition version 1.7.0.2 (and perhaps other versions) throw an error when you try to use the built-in product export feature. I've been able to find the particular product SKU's in my catalog that are causing the export routine to bomb, but I couldn't for the life of me figure out what was wrong with these records. I could not trace a specific condition back to the problematic records for something to blame, such as simple versus complex product types, attribute sets, funky characters or encoding, missing values - nothing. It seemed as if there was some sort of invisible problem with certain records that would cause the product export to fail.
I looked in the exception log and saw this super-helpful error message: