I had something like this before. Paypal in their wisdom took the money out my account, but issued it as an e-cheque for some reason which takes 7 days or something to clear. The seller would not get the money until it cleared, so I had to cancel the transaction and do it again. It went straight through the second time. No idea why the e-cheque to start with as it came straight out my account.
Perhaps this is the same situation for you?