Upgrade Framework 2.0 To 4.5 Issues

Hi 

I am facing a issue that is

When I have upgraded my Asp.Net Application of Framework 2.0 To 4.5 and I have upgraded the AJAX Toolkit from V 3.0.2 To V 15.1.4.0 

but still I am getting exception while i am making Response.Redirect In Update Panal That Is  "Error: Sys.WebForms.PageRequestManagerParserErrorException: The message received from the server could not be parsed"  in File "http://localhost:55727/ScriptResource.axd?d=AmR4Ge71vZWqb7MTSKsUz4TRpwYAV-v_VBADDy6S0-1_M1mce4J8bk3hR61Vdc5k4mXlcDL-ZyXxSyURQiU0LYxqcz_DvBYLZcXpA8pAWnSBmARPPoD2Jo7_od1w4MqNa0M3ndrib5PG0gPkbZuNcjYTDt_RQ8eiJg_uVKsb3ie1VIiSqjH7p_30nrbfZCHc0&t=72e85ccd:1435"

I need to Know How to Resolve this issue With generic  and what all modification we have to make on Web.config handlers so that it will function properly 

I Really needs Experts Advice As I am Stuck on the issue

Thanks 

Aakash