Zero cart totals

[musicmaster]

I have a problem with a updated/migrated website with the admin carts page.

When I look at it on my development computer I see a total value for each cart. However, after I uploaded to the server all carts had value zero. When I open a cart I see the products but they too are shown with value zero. Only new carts have a real value.

After some searching in the code I found that the problem happens in the function priceCalculation() in /classes/Product.php. This function contains the lines

if (!isset(static::$_pricesLevel2[$cacheId2][(int) $idProductAttribute])) {
	return;
}

and there the code execution takes the wrong turn and returns. The result is an empty price field.

I have no idea what this code is checking for and how I can fix this. Can anybody enlighten me?