Timeout expired and Unable to Login issue

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Hi Folks,

I am having this unique problem cropping up recently. User is trying to upload a file that has 25k rows. The application gives a time out exception as below.
Timeout expired. The timeout period elapsed prior to obtaining a connection from the pool. This may have occurred because all pooled connections were in use and max pool size was reached.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.InvalidOperationException: Timeout expired. The timeout period elapsed prior to obtaining a connection from the pool. This may have occurred because all pooled connections were in use and max pool size was reached.

Source Error:
An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

Stack Trace:
[InvalidOperationException: Timeout expired. The timeout period elapsed prior to obtaining a connection from the pool. This may have occurred because all pooled connections were in use and max pool size was reached.]
frmChecker.btnAuthorize_Click(Object sender, EventArgs e) +12004
System.Web.UI.WebControls.Button.OnClick(EventArgs e) +115
System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument) +140
System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) +29
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +2981
Version Information: Microsoft .NET Framework Version:2.0.50727.4927; ASP.NET Version:2.0.50727.4927

----END OF EXCEPTION------

Now when I go to the login page and try to login I am not able to login into the application. I am using IIS 7.5 in Windows Server 2008 R2 Standard and MS SQL 2008 R2.

I am able to login into the application when I re-start IIS. There are many apps hosted in this IIS Server and only my app seems to be affected by the above issue.

The same issue seems to exist in Production, UAT & SIT regions.

Please advice.

Thanks
Balaji.V