This is a pretty generic error message and can be seen for many different scanrios (if just google the error message you will find a lot of hits from pdn forums). Please match your scenario with the existing links first, if no luck, elaborate more your pega version and reproduction steps.
This issue got resolved and reason is with in modal dialog had couple of refresh. Then when refresh some point current thread get lost. Because of that we reduced some refresh with in modal dialog. thank you very much all comments that help me lots