The first (and this is the one irritating Netscape) is that it is saying question1 is undefined. And sure enough, if you look at the page, question1 is not a property of the window. The form question1 is a property of the document, so you need to change all your references to question1 to document.question1
The second (and IE has a problem with this too) is that if the user doesn't click any of the radio buttons, then the statement:
thisans = document.question1.q1[i].value
will never be executed and so the variable thisans will not be defined when you try to build the next page's URL...
window.location = "p2.htm" + "?x" + thisans
You should probably test whether testans == undefined before moving to the next page.