Paypal have been having major system problems since the 29th October, they had a complete outage and subsequently odd things have been happening in our account setups, some configuration settings on two of my companies biggest accounts dissappeared which resulted in us not getting confirmation that orders had been paid for.
From an end user perspective i'd avoid paypal for a week or so until everythings been back to normal for a while. We spotted the issues pretty quickly because we've a lot of money moving about but some smaller vendors who experience the same issues might not notice so quickly if they dont routinely check paypal.
Especially as Paypal havnt published anything relating to the configuration issue yet (which related to IPN details vanishing for those interested), only that there was an outage on the 29th.