Customer details missing from admin

Hello Forum

I have a strange problem in admin. When someone places an order (using Paypal standard), I go into the Sales>Orders section in admin where there are 5 tabs:

Order details appear okay
Payment details appear okay
But 'delivery details' - 'products' and 'history' all appear blank.

Can anyone suggest why this is happening?

I am using version 1.5.6.1 with zMaxcart theme

Cheers!

Seems I am wasting my time with this. 6 times now I have posted different questions in these forums asking for help. One question had one reply which was not the solution and the other 5 have not received a single reply. I used to use Zencart and found the forums there to be very useful and friendly but I'm really disappointed in the lack of response on here.