Quote Originally Posted by Daniil View Post
We've found the reason. There is a piece of new functionality in a RowEditing. It positions the buttons at the top if there is no enough space at the bottom. It breaks the things in Windows XP + IE8.

So, you could switch off this new feature by adding this into the page's <head>.
<script>
    Ext.grid.RowEditor.override({
        syncEditorClip: Ext.emptyFn
    });
</script>
Many Thanks Danil,
This worked.