Tax not working

I am setting up my checkout page and it’s not yet completely finished. However when testing my Shopping Cart I don’t see the Sub-total and Tax. I see only Grand total.
I see the Sub-total and Tax appear randomly when I do this:

I click on one of the ‘Add to Cart’ button, to simulate shopping, while in ‘Shopping Cart’ page I click on ‘Checkout’ button it directs me to ‘checkout’ page.
I fill in the Billing Information and check the ‘Same as billing address’ and click on ‘Checkout’ button.

I am redirected to a blank page that says: Table 'lumierep_cj.orders' doesn't exist.
I am not surprised to see this message because I did not finished yet the entire setup (this is not the problem).
From this page I click on ‘Go back one page’ (two times) in the Browser until I see Shopping cart and suddenly the Sub-total and Tax appear.
Can you please check out this issue? I want to make sure if I did something wrong in my setup or it’s probably an incompatibility between the eCart5 and some browsers.
Here is the link of my testing website:link removed

Please remove the link when you don’t need it.
Thank you.

I have the same problem in the below Browsers:
Mac:
Firefox 3.5.5
Safari 4.0.5

PC:
Internet Explorer 8
Firefox 3.6.3