Application pool is automatically stopped

Our web application hosted in .NET 2.0 and connected with oracle 10g xe . 800 to 1000 users are using the application.

Sometime 30 to 40 users are connecting to the application at the same time and the application pool is getting stopped.

In our custome error log, there are only one Application error generated by the application(due to oracle null reference exception ) .

But I would like to know what is causing the application pool to stop. I know I can set Rapid-Fail Protection to False.

The Event Viewer log:

Faulting application name: w3wp.exe, version: 8.0.9200.16384, time stamp: 0x50108835
Faulting module name: ntdll.dll, version: 6.2.9200.16579, time stamp: 0x51637f77
Exception code: 0xc0000374
Fault offset: 0x00000000000ebd59
Faulting process id: 0x1778
Faulting application start time: 0x01d21f3bac84235d
Faulting application path: c:\windows\system32\inetsrv\w3wp.exe
Faulting module path: C:\Windows\SYSTEM32\ntdll.dll
Report Id: ed34fd22-8b2e-11e6-9431-00155d023f14
Faulting package full name: 
Faulting package-relative application ID: