Sold an item. 'The following critical error has occurred'

[dotnet]

It's perhaps looking as if eBay got halfway through chucking out a bad buyer and seller, but didn't complete the job. Please advise!

Bidding ended. One bidder. I clicked on Send payment Details so I could send an invoice. I did my message requesting preferred payment method and clicked 'send' but it didn't go. I tried Contact Buyer and got 'The following critical error has occurred: the buyer's postal address cannot be found'.

When I tried clicking on my bidder's eBay monicker a different message came up: ' Sorry we encountered a problem. The feature you are attempting to access is not responding.'

I should say that somewhere along the line while the item was listed I got a message saying a bid had been cancelled. The message was about this same bidder, - but I made a guess and assumed he'd maybe put in an upper limit bid and then wanted to cancel that, - leaving the initial bid valid. It looks as if that was a bad guess.

So it looks as if there's no sale. When should I (should I?) relist? Do I need to do anything first? Thanks in anticipation.

[dotnet]

It's looking now as if it was some weird passing gremlin. I've managed to send my message - hopefully everything will go OK.
In my defence, another gremlin factor which caused panic was my first attempt to look at my buyer's feedback record. It said 'Positive feedback 0%; feedback score: 310'! The 'new' info, now I've gone back to verify what's what, shows 'Positive feedback 100%; feedback score: 310'...!
Scary, scary things, computers.