I think they lock down accounts which have sudden multiple large purchases as they may be consider suspicious activity and possible Fraud.
I believe a couple of members have run into it, and it was usually easily solved with an e-mail or a phone call.
you can contact them through their website here
http://www.fictionwise.com/servlet/mw?t=support
or
Fictionwise Inc.
Private Company, Headquarters Location
407 Main St., Chatham, NJ, United States
(973)701-6773, (973)701-6774 fax,
info@fictionwise.com
http://www.fictionwise.com
While it can be irritating, They are thinking of protecting your account.