There was an issue last summer with PayPal IPN, where they were rounding the cart total in the IPN callback, so that the IPN total was different than the original cart total.
These totals are tested to prevent "cart stuffing" with a second browser window during checkout.
This issue was circumvented in v7.0.2.0 by allowing up to a nickle difference between the original cart total and the IPN callback total:
Code:
if (NetTotal != PaymentTotal)
-- changed to --
if (Math.Abs(NetTotal - PaymentTotal) > 0.05M)
inside paypalok.aspx.cs and paypalnotification.aspx.cs.