Gridview Update Generates Full Page Postback

Question

I have a gridview within an update panel with autogenerateeditbutton=true. Modifying the gridview works fine with partial updates until the following:

1) Any validator is triggered 2) The offending control is corrected 3) Update linkbutton is clicked

At this point a full page post back is triggered instead of a partial.

The partial updates work as expected until after the validator shows an error. Then each subseqent postback is a full page post back until after the error has been cleared. After clearing the error clicking update, cancel or edit results in the expected asynchronous partial postback.

Any help is a appreciated.