asp.net firewalll isue?

Question

I am getting following error in asp.net. I am using following pages

1. UserControl having drodown list and grid view, gv is filled according to dropdown selection
2. master page using above control
3. aspx page using ,aster page with script manager.

Above code running fine in my WITHIN NETWORK. BUT when i check link at outside proxy following error appears

Sys.WebForms.PageRequestManagerParserErrorExeption error.The message received from server coulf not be parsed, the common cause of error are when response is modified by call to Response.Write(), response filters, HttpModules, or server trace is enabled.
Details: error parsing near '