In my experience this happens because of Paypal's poorly coded systems that fail to go through their security checks. I just got this when trying to transfer money from Paypal to my bank - 'Something seems to have gone wrong'. I believe that this happens when Paypal thinks it should do yet another check to validate you (absolutely ridiculous as you've logged in literally five seconds previously), but the software fails to bring up that check and therefore it just fails the process. I tried again two minutes later and it worked. Other than contacting 'support', who can't do anything because they're not given the tools by Paypal, I've not discovered any way to overcome Paypal's incompetence.
Edited to say, oddly enough, this basic failure to code happens on this very forum! When I submit a post and check 'I'm not a robot', it fails to post and says 'verification failed'. It only failed because it didn't bring up the image grid and give me a chance to complete the verification. It's exactly the same on the site. The transactions fail when Paypal tries to verify you but doesn't give you the chance to perform that verification. And of course Paypal don't care because they hold the customer in contempt.
