Magento - Random products being added to shopping cart

I have an issue at the moment where random products are being added to the shopping cart. They are being added when the user adds a legitimate item to the shopping cart. The problem appears random in that sometimes only 1 extra product will be added but other times there may be 2,3 or I have seen up to 11 extra products being added.

Additionally, I hav开发者_StackOverflow社区e noticed that the line totals for items in the cart are showing as doubled i.e. a product costs £21 and there is only 1 in the cart but the cart total is £42

Any ideas?

UPDATE: As an update, the issue is in the database somewhere. We have a test site which runs on a different database. If I move the database from the affected site to the test site then the test site also has the same issue

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We had a similar issue and think we have it fixed:

http://www.magentocommerce.com/boards/viewthread/295235/

SET FOREIGN_KEY_CHECKS=0; 
truncate sales_flat_quote; 
truncate sales_flat_quote_address; 
truncate sales_flat_quote_shipping_rate; 
truncate sales_flat_quote_address_item; 
truncate sales_flat_quote_item; 
truncate sales_flat_quote_item_option; 
truncate sales_flat_quote_payment; 
SET FOREIGN_KEY_CHECKS=1;

it might be related to your problem - hope it helps (try it on a backed up site / dev site first!!!)

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