Errors with Page Trace Enabled and ASP.NET AJAX

If you have page level tracing enabled on your site and you begin adding ASP.NET AJAX controls, you may see errors that say something along the lines of "Sys.WebForms.PageRequestManagerParseErrorException The message received from the server can not be parsed" when you preview or debug those pages. The ones I experienced appeared in a JavaScript alert popup.

If you have Trace="true" on the page in question, remove it. If you have your web.config file set for tracing, change it to: <trace enabled="true" localOnly="true" pageOutput="false" />

Browse or debug the page and then go to the root of your application's trace.axd file (http://yourapp/trace.axd) to get to the trace information.

See http://samples.gotdotnet.com/quickstart/aspplus/doc/tracelogapp.aspx for more.