Referal from eBay to paypal login using "Pay Now" button fails - a paypal page with "sorry an error just occured" message. Works in IE8 - problem since ff3.5.x as far as I can tell. Also similar problem with Amex site - so may be https issue.
As question, using "Pay Now" button in eBay and selecting Paypal as the payment method always leads to a generalised paypal error page with no specific details about the error. Always works in IE8. I also have problems with making payments on Amex's website. These also fail with a "Payment cannot be completed at this time try again later" message - using IE8 works so may be an https: issue. Have looked at issues connecting to secure sites on forum but info does not appear relevant to specific problem.
After much experimentation I have discovered that the most likely explanation for this behaviour is a subtly corrupted profile folder. I didn't fully identify the exact cause per-se but I now have an (apparently) fully functioning browser again with all my favourite add-ons enabled and I can buy stuff on eBay without resorting to IE - always a good day.