My sister has had her card used fraudulently from this data balls up.It was cleared up very quickly though, new card issued and refunds given. She has just found out though her credit rating has taken a big knock since and as yet doesnt know if it is related.
She should be able to find out what caused the hit on the rating (credit report should show it), and if due to the fraudulent activity get it corrected - either by the card issuer or by contacting Experian direct.