Intermittend Request Timeout and slow performance observed in .Net 2.0 application suddenly

Intermittend Request Timeout and slow performance observed in .Net 2.0
application suddenly

I have a strange problem occurring in one of my applications. The
application is .Net 2.0 and hosted on IIS 6.0 on a windows 2003 server.
This application has been running fine for the last 2.5 years. But
suddenly since Aug 15th, we are facing intermittent performance issues and
request timeout. The page load takes minutes, some time we get Request
timed out error and sometime the page just loads on and on without getting
rendered. This is purely intermittent and occurs anytime suddenly while
navigating any page and there is no defined pattern observed. All other
times the same code and navigation works perfectly fine. The frequency of
this intermittent performance has increased over the last few days.
There is a separate app pool in IIS httpRunTime ExecutionTimeout Setting
is set as 250 No of users accessing the application ~100
I know increasing the httpRunTime ExceutionTimeout setting would make this
error not getting logged. But the goal is to know why and where the pages
are timing out suddenly since the last few weeks and to make the
performance faster all the time without any intermittent issue. Is this an
IIS/Memory pool/Worker Threads exhausted issue. If yes, can some settings
be changed to make the application perform faster?
Also the DB is fine and the queries are executing fast. No issues there.
And there are no memory leakage codes in the application as well.
A sample EventViewer log is as below
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Event code: 3001
Event message: The request has been aborted.
Event time: 9/5/2013 4:20:24 PM
Event time (UTC): 9/5/2013 8:20:24 PM
Event ID: cbc5ec25d6de466680c5e3575726b8dd
Event sequence: 358
Event occurrence: 1
Event detail code: 0
Application information:
Application domain: /LM/W3SVC/4262/ROOT-1-13022880541327
Trust level: Full
Application Virtual Path: /
Application Path: E:\inetpub\wwwroot\Myapp\
Machine name: mymachine
Process information:
Process ID: 252
Process name: w3wp.exe
Account name: NT AUTHORITY\NETWORK SERVICE
Exception information:
Exception type: HttpException
Exception message: Request timed out.
Request information:
Request URL: myapp/page.aspx
User host address: ip address
User: userid
Is authenticated: True
Authentication Type: Negotiate
Thread account name: NT AUTHORITY\NETWORK SERVICE
Thread information:
Thread ID: 5
Thread account name: NT AUTHORITY\NETWORK SERVICE
Is impersonating: False
Stack trace:
Custom event details:
For more information, see Help and Support Center at
http://go.microsoft.com/fwlink/events.asp.
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Any help is highly appreciated as we are facing lot of escalations from
clients on this issue and we need to solve this issue at the earliest.
Thanks, VijayGanesh