Getting "Time out expired or server not responding error" in asp.net web site

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database

session

execution

Hi,
We are using 4 time outs in our application to keep it from throwing timeout error
1. Connection Timeout=6000
2. SqlCommandTimeOut = 6000
3. httpRuntime executiontimeout = 600000
4. SessionState Timeout = 1440

As you can see we have set pretty high time for each time out, we didnot anticipate the timeout error to popup. But unfortunately the "timeout expired or no response from server" is thrown. This happens when a particular SP executes. I have used the profiler to fetch the query and ran it directly in the sql server management studio, it took 3 min 44 secs to get the data and in the end did not even throw any error. But when the same is run from the website , the website is throwing error. Can you please suggest what went wrong.

Note:- The SP used is dynamic. I mean it contains a lot of dynamic sql.
Our application in written in ASP.NET.