popup window wont open from my info window

why is it that the following html doesnt work in an infowindow?

var html = '<div style="width: 200px"><form method="post"
action="test.php" style="margin-bottom:0px;"><table border="0"
cellspacing="0" cellpadding="0"><tr><td colspan="2"><b>' + heading +
'</b><input type="hidden" name="type" value="' + heading + '"><input
type="hidden" name="coordinates" value="' + point +
'"></td></tr><tr><td>Name:</td><td><input type="text" name="name"
id="name" size="23" maxlength="30"
/></td></tr><tr><td>Link:</td><td><input type="text" name="link"
id="link" size="23" maxlength="50"
/></td></tr><tr><td>Email:</td><td><input type="text" name="email"
id="email" size="23" maxlength="40"
/></td></tr><tr><td>AIM:</td><td><input type="text" name="aim" id="aim"
size="23" maxlength="25" /></td></tr><tr><td colspan="2"><textarea
name="comment" cols="23" onfocus="doClear(this);" wrap=hard>Enter your
comment here.</textarea></td></tr><tr><td colspan="2"><input
type="submit" value="Submit" /><input type="button" value="Preview"
onclick="popUp(\'preview.php?type=' + header + '&name=' + name.value +
'&link=' + link.value + '&email=' + email.value + '&aim=' + aim.value +
'&comment=' + header + '\')" /></td></tr></table></form></div>';

NOTES
=====
1.All variables that are referenced have been set in other places in
the script.
2.The table isn't whats causing the problem. The info window loads
without:
<input type="button" value="Preview"
onclick="popUp(\'preview.php?type=' + header + '&name=' + name.value +
'&link=' + link.value + '&email=' + email.value + '&aim=' + aim.value +
'&comment=' + header + '\')" />

so whats the issue here?