It was brought up by Wyatt that 2-factor auth ("security key") login in the new MUUG PayPal payment system does not work. It won't let you login. Note, if you don't know what 2-factor auth or PayPal's "security key" is (hint: it's not your "password"), then you aren't using it and you can ignore this notice.
It seems PayPal is aware of this bug, and are working on putting 2-factor auth into all their API's, including the one MUUG is using. Who knows when they'll get it done.
I did find a new workaround that might help:
Login to PayPal first, manually, using your 2-factor auth, by going to their main page. Then access the MUUG payment interface before you timeout (around 10 minutes). It may just let you skip the login completely via the MUUG links.
The only other option is to go into PayPal manually and disable 2-factor auth before you use the MUUG system.
Also, you can always skip the login completely and use the "buy as guest" option to enter your card details directly.
From a quick show of hands it appears less than 5% of our users are
using 2-factor, so for the time being we'll just be hoping PayPal fixes this bug soon.