Sys.WebForms.PageRequestManagerParserErrorException: The message received from the server could not be parsed.

Hi,

I have update panel in my application. When I click button inside update panel then it reflect the following error.

Unhandled exception at line 885, column 13 in http://localhost:56054/ScriptResource.axd?d=HJpd8Ecopg7f8I5z3pbAzO4plde4scM1l8HNVijSoJ5TAcuhA-lN6EwvzzcDTPDjShVwXf_pqBEHpUNoT8LXX5YzbVSV6o_JRMCb7UNO96K_UTn7Kr9XX-vNkMJbnHO8iiyeRp39KZxX1CRT_subfdiIynwc4R7eoS4sWQ99w5qWuvCGr90HDnBsb9Dmo7Dq0&t=ca758f3

0x800a139e - JavaScript runtime error: Sys.WebForms.PageRequestManagerParserErrorException: The message received from the server could not be parsed.

-- I did not modified my response from anywhere.

-- I have complete form without any tag mismatch