Vista - random I got system.nullreferenceexception error

randomly I got system.nullreferenceexception error from my website CMEBSV10,
and then I will receive another error xml.xmlexception the root element is
missing. But this webiste runs very well in other computer. I reinstalled the
OS two times in this computer(the server we use). As I have no other servers
to use, so I must make this computer works well with CMEBSV10. EVENT LOG:
3005
ADD:
OS:WSE 2003

Event Type: Warning
Event Source: ASP.NET 2.0.50727.0
Event Category: Web Event
Event ID: 1309
User: N/A
Computer: Webserver1
Description:
Event code: 3005

I have search the solution from Google for almost 2 weeks and find nothing
useful.

Thanks for your time for giving me some suggestions!

Hello davidhao,
In a worst case scenario, deploy a debug release to the server and check
which line of code is giving you the nullreferences. Also, is there any functionality
which isn't working? Are you getting error pages anywhere? That would also
lead you to the cause.

It's probably a programming error, maybe related to the number of users using
the application.

It is very hard to say without more detailed information and googling won't
help you, neither will posting here if you haven't got a more substantial
description of what's going on...

--
Jesse Houwing
jesse.houwing at sogeti.nl