I think I had this problem long ago.  If my memory is correct, this is what caused it. I had an error in my code. 
Here is a pseudocode sample:
<form name="myform" onsubmit="return true" action="/cgi-bin/waa1gate.isa" method="POST">
...blah, blah, blah code
<input type="button" value="Continue" onClick="document.submit();" />
</form>
 
This caused the form to be submitted twice, once by the javascript function, and once by the form method.  I think it was confusing many tasks, and eventually WAA1SRV.exe was giving up.
 
My solution was to change the form tag attribute to onsubmit="return false" and suppress the second instance.
I do not use <input type="submit"...>; I prefer the flexibility of using javascript for this task.