Solution in earlier post I believe: http://larryullman.c...iger#entry20448
highlights of my 'workaround':
I had the same problem. It seems 2 problems:
Fisrt, qty can get truncated to 127 or 255 in the database. Had to change the type to mediumint(8) to reliably enter semi-reasonable quantities into MYSQL. Couldn't find a mismatch between collation, character sets, it all seemed consistent at UTF8-general, but maybe I missed something there. Had to change to mediumint(8) in the database tables AND stored procedures (qty parameter definition).
This first problem affects both the cart and the wishlist, have to fix both places.
Second problem, calculating the subtotal fails when in thousands because the number format function returns a string with the comma.
echo '<br>' . 'price is ' . $price;
The inherent typecasting to INT apparently is truncating to just the thousands digit. Found this fix online, just insert in cart.php (and wishlist.php) after the get_just_price function but before the subtotal calculation:
$price = htmlentities($price); //important part
$price = str_replace(array('&#36; ', ','), '', $price); //remove $ and comma