This is usually a case of multiple form fields on the previous page with the same name. For example, if you have a form with the following:
<input type=text name=a value="whatever"> <input type=text name=a value="whatever else"> |
When you response.write(request.form("a")), it's actually going to return the following:
If this happens, scan through your form looking for multiple instances of that input field name.