PayPal rolls out update which breaks all payment links

As of about 9 hours ago, PayPal has rolled out a new website and now anyone trying to purchase one of my products via PayPal will see a "Page not found" error upon arriving at PayPal.

I’ve already contacted PayPal but until this problem is solved please consider using Kagi instead, or just go to PayPal and send me a payment with a description of the product that you’d like to buy. You can do this using the "Send Money" tab at PayPal and sending your payment to win@wincent.com. Apologies for the inconvenience!

Update

Still no word from PayPal but through trial and error I’ve been able to get the links working again. If you’re selling online and have been hit by this problem see my notes on the solution.