There are two problems in your script...
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.