But actually doing
<p><%=PostNo%> required posts.</p> is much more entertaining than the long way
Are you trying to cast a number larger than 32,000 to an integer?
I've had similar problems when dealing with regional settings for decimal seperators and the thousands, but that doesn't seem to be the case for you...
Usually you get this error when you are over the limit on Request.Form. ASP's limit for form processing is supposed to be about 100k, according to Micro$oft, it breaks down further to a max of 102,399 bytes for each field. Which, again, doesn't seem like it should be affecting you, depending on what you are sending into the form...if it is the case, however, you can always use the old dirty trick of using your own function to deal with the form handling and therefore get around the overflow fatality.