error with paypal payments on site

Hi,

Ive just started getting the following error when customers try to pay on my site:

Error while placing order. Error 1: Payment error: LongMessage: This transaction cannot be processed. The merchant's account is not able to process transactions. ShortMessage: Invalid Configuration ErrorCode: 10548 .

It has been working fund before and I have touched the site for a while, paypal is all set up and the api settings are correct on the site.

I'm running V3.8, any ideas?

Thanks

10548  This transaction cannot be processed. The merchant's account is not able to process transactions.
  The merchant account attempting the transaction is not a business account at PayPal. Check your account settings.

https://www.paypal-knowledge.com/infocenter/index?page=content&id=FAQ1147&actp=LIST