The best way to solve this problem programmatically is to
Import the product
Examine all the product's attributes via some custom code
Save the product
Examine all the product's attributes via some custom code
Compare the results of #2 and #4
Ensure your import process explicitly sets whatever attributes were missing in #2 but present in #4
Here's the snipping I'd use to examine the product attributes. Run this or something like it in a phtml template, custom controller, etc.
var_dump(
Mage::getModel('catalog/product')
->getCollection()
->addAttributeToSelect('*')
->addAttributeToFilter('sku','SKUGOESHERE')
->getFirstItem()
->getData()
);