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I have tried to pay an invoice via BitPay, the transaction was stuck at 'seen by one peer' and the BitPay invoice expired.
After closing and reopening multibit a few times, I decided to reset blockchain info as suggested in the multibit faq.
Well, this is what happened:

The transaction to BitPay doesn't even show anymore, but my coins are gone, how do I get them back ?
Before you do anything else, check whether you made the payment or not. Use blockexplorer or a similar authoritative tool. – David Schwartz – 2013-12-10T04:16:27.433
@DavidSchwartz there is no information about the transaction to BitPay on Blockexplorer / Blockchain.info, but my coins are still not showing – Dieter – 2013-12-10T13:02:41.897