Problem to product page

Hi,

i have a problem with product page.

when compiler is enabled then magento displays white screen on product page.
if compiler is disabled then displays 404 error page.

i commented out the line

$defaultheme = Mage::getStoreConfig(‘design/theme/default’,"default")?Mage::getStoreConfig(‘design/theme/default’,"default"):"default";

from the /app/design/frontend/default/jm_mago/template/catalog/product/view/media.phtml file, then displays the product page and it seem to work fine.

i think this line that i commented out, may couse other problems and i want to find the appropriate solution.

thank you in advance.