Time Out When Exporting Matrix Report To Excel

I ran a matrix report and chose to export it to excel. It was taking a very long time and then the error message below popped up. I can export other matrix reports to excel. Can someone shed some light on where I might determine is the cause of the problem?

Thread was being aborted.
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.Exception: Thread was being aborted.

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:





[Exception: Thread was being aborted.]

[Exception: An error occurred during rendering of the report.]

[Exception: An error occurred during rendering of the report.]

[Exception: The operation has timed out. The report server has canceled the operation.]
Microsoft.Reporting.WebForms.ServerReport.ServerUrlRequest(Boolean isAbortable, String url, Stream outputStream, String& mimeType, String& fileNameExtension) +882
Microsoft.Reporting.WebForms.ServerReport.InternalRender(Boolean isAbortable, String format, String deviceInfo, NameValueCollection urlAccessParameters, Stream reportStream, String& mimeType, String& fileNameExtension) +1312
Microsoft.Reporting.WebForms.ServerReportControlSource.RenderReport(String format, String deviceInfo, NameValueCollection additionalParams, String& mimeType, String& fileExtension) +215
Microsoft.Reporting.WebForms.ExportOperation.PerformOperation(NameValueCollection urlQuery, HttpResponse response) +204
Microsoft.Reporting.WebForms.HttpHandler.ProcessRequest(HttpContext context) +137
System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +499
System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +177