problem with modal dialog pop up .

I am using custom V5.master for my site.

Problem I am facing is with Modal dialog pop up.

I have created a calendar list and added it on a webpart page.

I try to create new event, on that webpart page, by clicking on add new event. In the pop up some fields in the top appears behind ribbion. And this does not happens when logged with system account.

regards, Ritesh Anand