An unhandled exception has occurred

我有一个在线运行的web站点，时不时会出现在线人数下降的情况，网站情况：
基于.net 3.5，c#开发，部署环境：win server 2003， iis6.0 asp.net2.0。

检查在线下滑的时间段，发现iis服务器的中大量存在下述事件信息，类型为warning

Event code: 3005 

Event message: An unhandled exception has occurred. 

Event time: 6/22/2011 5:48:29 PM 

Event time (UTC): 6/22/2011 10:48:29 AM 

Event ID: 166b3c2bce9f4171a830d6fc9ffc58f9 

Event sequence: 6002 

Event occurrence: 3001 

Event detail code: 0 

 

Application information: 

    Application domain: /LM/W3SVC/1282155927/Root-2-129532126469053750 

    Trust level: Full 

    Application Virtual Path: / 

    Application Path: D:\web\request\ 

    Machine name: GS_GN_04_WEB 

 

Process information: 

    Process ID: 2312 

    Process name: w3wp.exe 

    Account name: NT AUTHORITY\NETWORK SERVICE 

 

Exception information: 

    Exception type: TypeInitializationException 

    Exception message: The type initializer for 'Tank.Request.Global' threw an exception. 

 

Request information: 

    Request URL: http://www.gn.zing.vn/CreateLogin.aspx 

    Request path: /CreateLogin.aspx 

    User host address: 123.30.133.144 

    User:  

    Is authenticated: False 

    Authentication Type:  

    Thread account name: NT AUTHORITY\NETWORK SERVICE 

 

Thread information: 

    Thread ID: 9 

    Thread account name: NT AUTHORITY\NETWORK SERVICE 

    Is impersonating: False 

    Stack trace:    at Tank.Request.Global..ctor()

   at ASP.global_asax..ctor() in c:\windows\microsoft.net\Framework64\v2.0.50727\Temporary ASP.NET Files\root\b11f52b4\54c71dd4\App_global.asax.dr5yzzkb.0.cs:line 0

 

 

Custom event details: 



For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp.

请问这是什么问题引发的啊？

另外我在global.asax.cs中实现了Application_Error()接口以捕获异常信息，结果发现类似这样的异常还是捕获不到，或者说是绝大多数时间不起效，只是很偶尔的时候起效。

以上问题，求高手指点。