on the checkout page, you have the following code at lines 47 - 58:
<%
if (WA_eCart_IsEmpty(QuoteCart2)) then
QuoteCart2_redirStr = "mybasket.asp"'_redirStr
QuoteCart2_cartAction = "RedirectIfEmpty"
end if
%>
<%
if (WA_eCart_IsEmpty(EFTCMain)) then
EFTCMain_redirStr = "mybasket.asp"'_redirStr
EFTCMain_cartAction = "RedirectIfEmpty"
end if
%>
it looks like you have 2 cart objects in your site, EFTCMain, and QuoteCart2. This code will set the cart to redirect to the mybasket.asp page if one of those carts is empty. you should probably remove the redirect code for the quoteCart2 object:
<%
if (WA_eCart_IsEmpty(QuoteCart2)) then
QuoteCart2_redirStr = "mybasket.asp"'_redirStr
QuoteCart2_cartAction = "RedirectIfEmpty"
end if
%>