I went searching for a tread like this one because I just ran into a frustrating problem with IE7 after installing NIS 2007 (just as my NIS 2006 subscription was expiring). The problem was that IE7 in all other XP PRO user accounts (regardless of their rights!) generated script errors on many sites (e.g. hotmail) and/or did not display everything on those sites (e.g. Dell).
Despite the fact that the problem started at exactly the same time that I installed NIS 2007, the Symantec techs gave me the same story: "if you've turned everything off an you still have the problem, then it's not our software".
There an MSDN thread
here that describes the IE7 scripting errors that some people are having and the fixes they are trying. You'll see that a number of people started having these problems after installing Norton.
It seems that there is some sort of compatibility problem between IE7 and Norton. I had to finally uninstall IE7; all the user accounts are again working correctly now that we're back on IE6. I tried reinstalling IE7, but the problem immediately returned. I have no explanation for the fact that I had been running IE7 with NIS 2006 without any problems all this year.
The bottom line seems to be this: if you experience any kind of IE7 browser problem, you may have stumbled into this compatability with Norton. If you want to keep Norton, you may need to uninstall IE7 and live with IE6 (I already miss the tab feature) or pick up Firefox or Opera.