ntoskrnl.exe issue

["R M" <whisk3y () hotmail com>]

All

We have a w2k small business server installed with Exchange 2000, ie 5.5, 
ISA 2000 [acting as a proxy server + packet filter], webshield & netshield 
4.5.

The ISA packet filter was configured to permit outbound http and two way 
smtp traffic.   2 of our servers crashed yesterday afternoon and we are now 
receiving error messages about the ntoskrnl.exe is missing or corrupt.

This is odd considering the two servers went down at similar times in two 
different remote locations.

The anti-virus software was bang up-to-date with the latest engine and dat 
files but I still think this may be some sort of vulnerability - can any one 
help please?

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