shopping cart display items error

Hi, I need help to fix this. Whenever i add items to cart, it kept displaying wrong amount of items added, however this applied to removing items from cart too.

For example (add item to cart error):
add first item - works fine (show 1 item added)
add 2nd item - it shows only 1 item in the cart
add 3rd item - sometimes it show 2 items in the cart, sometime only 1 item.

For example (delete item from cart error):
Let say i added 5items but only 3 items show in the cart. I deleted the 3 items then the other 2 items show-up in the cart. After i remove the 2 items, sometime all 5 items show-up.

I been searching for solutions but nothing works. So far I had tried

1. Add php_flag register_globals Off in htaccess
2. Turn off register_globals php.ini (root and admin)
3. add /xxx/xxx/xxxxx/cgi-bin/tmp; in php.ini


Version: 1.5.1.3 opencart (fresh install)
Mod: only install vqmod 2.1.5 / Auto-Fill_Model_Number

Ps: Everything works fine in localhost

Please help............. Thanks!!!

Sorry for not include link. However I have fixed it.