This problem is usually related to the shipping details being incorrectly entered.
After the customer enters their shipping details, Interspire Shopping Cart tries to contact your shipping provider to obtain a real time shipping quote. If the details are not correctly configured in the Shipping Settings section then the shipping provider will respond with an invalid response. The checkout page will continue to wait for a valid response and eventually times out.
To check that your shipping details are correct go to the Shipping Settings part of the admin section. Then click on Shipping Zones tab and click edit on the appropriate zone. Once you are in the Shipping Zone section, click on the Shipping Methods tab and edit your shipping provider.
Please check that all your details are entered correctly and that you are able to obtain a test shipping quote by clicking 'Get Shipping Quote'

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