Multiple Modal Popup Extenders on the Same Wizard Page

I need to have three modal popup extenders on the same wizard page. Two of them will be in the same gridview. Because I need access to the server side both before and after the popup, I did not sent the OK Control ID. For the pop ups in the datagridview, the target control id is a dummy button.

I have no problem when one modal popup extender is placed on the page, but when I put the second one on, the server-side event stops firing, and the pop up  never appears.

Is there a problem with multiple modal popup extenders on a page or am I doing something wrong?

Thanks!