PageRequestManagerTimeoutException

I have an upload control that works fine on several servers. On one server it seems to upload files as normal, but the progress gets stuck at 92% and eventually comes back with a javascript error 'Sys.WebForms.PageRequestManagerTimeoutException'.  The files are small, and the server and connections high spec so it is not a problem there.
After it has done this it is necessary to recycle the application pool as it hangs the website.
I am not getting any exceptions thrown, or anything in the event log.

Have you any guidance as to how to investigate this problem?

Could it have anything to do with things like IIS lockdown tools or Baseline security analyzer?

Hi Simon831,

This is the first time we get a report for such a problem since we changed RadUpload's file handling logic and to my regret I can't help with a direct advice. Actually now the uploaded files are handled by the ASP.NET engine itself, while RadUpload just monitors the file upload process.

The client-side TimeoutException is thrown after the server-side part of an Ajax call has taken too much time to complete. It seems that some object gets locked on the server, thus preventing the process completion.

By the way, RadUpload does not use ASP.NET Ajax calls to update the progress area, but instead it uses pure XmlHttp calls. Am I missing something in your scenario?

Kind regards,
Erjan Gavalji
the Telerik team