System.CannotUnloadAppDomain

Error in Event Viewer - Application.
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The description for Event ID 5000 from source .NET Runtime 2.0 Error Reporting cannot be found. Either the component that raises this event is not installed on your local computer or the installation is corrupted. You can install or repair the component on the local computer.
If the event originated on another computer, the display information had to be saved with the event.
The following information was included with the event:
clr20r3
w3wp.exe
6.0.3790.3959
45d6968e
system.web
2.0.0.0
4333aecd
5ce
47
system.cannotunloadappdomain
NIL
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Possible causes:
-Server out of resources - low memory (RAM), low disk space
-Asynchronous processes unable to be terminated
-IO operations blocked (socket etc)

Why it happens:
IIS tries to recycle a w3wp.exe (due to unhealthy, deadlocked, db timeout states) and cannot unload it due to one of the above reasons. IIS then decided to kill that process in a 'brutally' way and log this kind of error.

Is it wrong?
Usually start with a few errors per day and can end into a crash at each 4 minutes if you have low hardware resources and lot of load (more than 4000 requests)

Temporary fix
Upgrade RAM, check disk space then go for webgarden and in a short time to webfarm.