I had the same issue. Bought 1000 CP especially for the Black Friday sales. Tried to purchase TOS U.S.S. Enterprise, but the same error message came up for me. I was trying to purchase it on my Federation Commander character at the time, but once I started a new character I was able to buy the ship. It's a pretty nice ship with blue phasers, shame the Photon Torpedoes are still red though, if memory serves they were blue in TOS right?
Basically, try buying the items on a lower level character.