Maybe we have sure a careless mistakes, not a bug!
at v. 1.40 ProductVariantTierPrices.ascx file on delete button we have:
<asp:Button ID="btnDeleteProductVariantAttribute" runat="server" CssClass="adminButton"
Text="Delete" CausesValidation="false" CommandName="<% $NopResources:Admin.ProductVariantTierPrices.Delete %>"
ToolTip="<% $NopResources:Admin.ProductVariantTierPrices.Delete.Tooltip %>" />
and delete not work, than edit in:
<asp:Button ID="btnDeleteProductVariantAttribute" runat="server" CssClass="adminButton"
Text="<% $NopResources:Admin.ProductVariantTierPrices.Delete %>" CausesValidation="false" CommandName="Delete"
ToolTip="<% $NopResources:Admin.ProductVariantTierPrices.Delete.Tooltip %>" />
and now work :)
perhaps there was a substitution between Text and CommandName property.
Bye