coupons applied in checkout to items they aren't meant to discount causes serious error

Hello, the scenario is: coupons are enabled for some items, but not others, and the user is checking out for the purchase of an item for which coupons are not enabled. On the checkout screen, if the user attempts to apply the coupon anyway, they get a good error message immediately below the coupon field saying "You do not have applicable products in your cart.", however, they ALSO get this message in pink at the top of the page when they click "Review Order", which prevents progress to the next screen, and there is NO WAY for the user to recover from this error, not to mention that it lacks context. The only possible recovery is to return to the shopping cart and start again (even reloading the checkout page doesn't work), so this will almost certainly mean losing customers who mistakenly try to apply coupons during checkout to items for which the coupon doesn't apply.

This error message works fine in the shopping cart, just not during checkout.