Even though you didn't mention Javascript at all this very much sounds like a Javascript issue.
The easiest thing to do would be to use an HTTP monitor. If you are using Netbeans there is one included already. Otherwise you could use VisualProxy. You can get it at
http://www.visualproxy.org. Using an HTTP monitor you can see how many request your client really issued (and of course which parameters, headers and so on - though this information is not relevant for your problem).
If - as I assume - you are actually sending the form twice it might be because you submit your form using Javascripts form.submit() and event propagation is not prevented properly (meaning that the browser also submits the form as usual - and thus you get two submits).
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Wolfram Rittmeyer
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