I have an account that has Paypal established to it, and haven't had a problem in years. I got an email yesterday saying that they couldn't migrate my billing information to thier new system so I would need to reenter it. To make sure it wasn't a scammer I went to the site direct instead of through the email, and it did appear that the PayPal was missing. So i reentered it. Today I tried SEVERAL times to make Linden purcases, and everytime it would crash out saying it was cancelled.
I spoke to a person with LL, who said that it was a recent and known bug as of Thursday and they were working on it. I am adding this information here in the hope that any updates will also be added here.