Problem in Creation of Activity Request Questionnaire

Hi

I'm facing issue while creation of activity Request Questionnaire. After setting the status to complete & Clicking 'Ok' the activity is not getting created. Its showing 'Internal Error'

When I checked in Tcode SLG1 for error log, I'm getting following error.

I was not facing this issue with other activities. But when i use Request Questionnaire activity I'm facing the problem. The worst part is when i use this activity, all other activity start showing same problem i.e. if i skip Request Questionnaire & use other activity every thing works fine.

Please suggest

Regards