Yeah this happened to me as well. The 31 days is only for new accounts and only happens once; this was suppose to take effect on May 1, but it took them until just a few days ago to put it into action.
I created my account on May 11 at CampBX (got verified in less than 12 hours) and did two transfers from dwolla (500 and 700), bought bitcoins and then transfered to my wallet. My third deposit, 2 days ago, is now under their new hold policy. I don't understand CampBX, as Dwolla changed their policy where users can no longer chargeback for e-currency transactions. But whatever
Just have to wait it out as they say it is a one time thing.
I transfer funds in and out of CampBX with Dwolla all the time and don't have any issues. I think i created my acct in April though.
And the 30 day thing is supposed to be about transferring BTC out of CampBX. So maybe there is something new I'm not aware of it but post a link or copy/paste so we know what you are talking about.