The reason was simple. Did you guess already?
Yes, that was the former and noisy for almost every web developer browsers compatibility issue. There are no any problem with FireFox and Google Chrome. The only Internet Explorer (I tested versions from 6.0 to 8.0) automatically replaces ‘©’ part in the ‘©_from_user_role’ URL parameter name inside JavaScript code to the copyright © sign. That’s invalid role name inserted into WordPress database and the whole user roles and capabilities list crashes as a result. To isolate this problem I should use other name for this URL parameter – user_role_copy_from.
Wow!!! It started work as expected. Thank you, darling Microsoft.