There have been a number of fairly widely applied "security fixes" in both Windows/NT and Linux/Unix systems. It's entirely possible that the ISP felt obligated to apply a "security fix" that has the potential to affect users of the various browsers in different ways. They would probably get any such "fixes" from sources who have "confirmed" them for the more common browsers, but may not have the resources to "confirm" - and develop corrective action - for all the browsers that may be in use.

The ISP statement that they "support" IE and Netscape probably does mean that they have confirmed that these two browsers will still work, although it's not necessarily a guarantee that you won't need some adjustments. It almost certainly means that they can, and are willing to, provide any necessary "resets" needed - if you're running one of these browsers.

I don't have details on all of the recent "fixes," but it is not uncommon, when the server applies a fix, to need a corresponding fix or adjustment of settings on users' machines. With the exception of the few common browsers that the ISP "knows" well enough to pass on "second hand information," the proper place to get the needed software mods is from the software manufacturer. Even if the ISP can make your IE and Netscape work, you might be well advised to check with the IE and Netscape "makers" for more complete fixes - in the case of something like this (apparently) major ISP change.

The "invalid page fault" frequently does indicate file corruption on your machine, so reinstalling your browser is a logical step (although not necessarily the most/first logical one). The first step is to seek support from the software manufacturer.

Why do ISPs change these things??:

"A recent research note from two analysts at the Aberdeen Group calls open-source software and Linux distributions the "2002 poster children for security problems." Of the 29 advisories issued through October by the CERT Coordination Center at Carnegie Mellon University in Pittsburgh, 16 of them addressed vulnerabilities in open-source or Linux products." ZiffDavis bulletin

John