AJAXTOOLKIT PROBLEM in INTERNET EXPLORER 10

Hi everybody!

I have a website in wich I have used Asp.net AjaxToolkit modal popup element,

It worked fine on every browser, but recently I tested it on Internet Explorer 10 (on windows 8 platform), and discovered a problem,

when I open a modal popup, the popup content is not loading and a message box is appearing with an error like this:

"Error: Sys.WebForms.PageRequestManagerServerErrorException: Input string was not in a correct format."

Anyone heard about this error?

What is going wrong, what kind of "Input string" I was prompted about?

Write an answer please, if you know what the problem is.

Thanks in advance.