Use attached to reproduce (just start it and press enter).

Workaround:

class MyBehavior : VirtualGridInputBehavior
{
    public MyBehavior(RadVirtualGridElement element) : base(element)
    {

    }
    protected override bool HandleEnterKey(KeyEventArgs keys)
    {
        if (this.GridElement.CurrentCell != null)
        {
            return base.HandleEnterKey(keys);
        }
        return false; 
    }
}


radVirtualGrid1.VirtualGridElement.InputBehavior = new MyBehavior(radVirtualGrid1.VirtualGridElement);