AJAX :: MaskedEditValidator Outside Gridview Disable Delete Command In ItemTemplate Field

Something "weird" is happening with my ASP.NET application. I have a MasterPage with WebForms, and inside one of them, I have an ASP TextBox which is controlled by the MaskedEditExtender/MaskedEditValidator couple. Underneath, I have a GridView with 2 columns, an Edit ASP Command Field, an ItemTemplate which contains an ASP ImageButton with a Delete CommandName linked to a GridViewDelete Event through the OnRowDeleting attribute. The GridView is binded with SQL Server data while the page is loading.

It appears that once the page is loaded, if I want to delete a row by clicking on the ASP ImageButton, nothing appears. I have first to do something else with the GridView (raise an Edit Event for example), then it's accessible. I try different stuff to catch the source of the problem, and the "weird" part appeared when I deleted the MaskedEditValidator, just keeping the MaskedEditExtender : the Delete ASP ImageButton worked since the page loads!