Sometimes you may see an error like the following when you have an ASP.NET application that has crashed, an event message that is similar to the following may be logged in the System log:

Event Type: Warning 
Event Source: W3SVC 
Event Category: None 
Event ID: 1009 
Date: 9/28/2005 
Time: 3:18:11 
PM User: N/A 
Computer: IIS-SERVER 
Description:
A process serving application pool ‘DefaultAppPool’ terminated 
unexpectedly. The process id was ‘2548’. The process
 exit code was ‘0xe0434f4d’.

Additionally, an event message that is similar to the following may be logged in the Application log:

Event Type: Error 
Event Source: .NET Runtime 2.0 Error Reporting 
Event Category: None 
Event ID: 5000 
Date: 9/28/2005 
Time: 3:18:02 PM 
User: N/A 
Computer: IIS-SERVER 
Description: 
EventType clr20r3, P1 w3wp.exe, P2 6.0.3790.1830, P3 42435be1,
P4 app_web_7437ep-9, P5 0.0.0.0, P6 433b1670, P7 9, P8 a, 
P9 system.exception, P10 NIL. 

The resolution is documented in:
http://support.microsoft.com/default.aspx?scid=kb;EN-US;911816

There was a change for 2.0 so if there is an unhandled exception that occurs outside of the context of a request.  If they are inside of a request, they will get wrapped into an HttpException and this won't happen.

There are a couple resolutions there, the easiest is to just change back to the 1.1 behavior by adding the following code to the Aspnet.config file located in the %WINDIR%\Microsoft.NET\Framework\v2.0.50727

<configuration>
    <runtime>
        <legacyUnhandledExceptionPolicy enabled="true" />
    </runtime>
</configuration>