only if criptsy is on the right chain
An internal trade is one that someone has already sent and been confirmed as being "on the right chain".
Unless the fork is longer than the number of confirms... but by that point, it is already too late anyways, those have already been traded and would be lost at that point. If you know there is a fork, and you know where it is... roughly... you know which coins to "not trust" that came-in beyond block-x or within x-blocks...
But if someone deposited 20000 blocks at 5000-height, and the fork is 7000+... then you can safely allow those coins to move to any internal account on an exchange. Since those coins are not physically moved in a wallet, just tracked by the database as having a new owner.
When you trade CAP for BTC on an exchange, you don't get it instantly deposited into a personal wallet. It stays in the exchanges wallet, until you decide to withdraw it to your external wallet. Then it just checks that you are the owner, and if you are, they get pushed to a block for withdraw.
Internally, issues with a wallet only impede deposits, because someone may be depositing on the wrong chain, which is not detected by the other chain. (So it can't be collected, or would be erased if it came in after the fork, from another block, or didn't come in at all.)
But internally, it doesn't matter. On an exchange. (Not to a trader, who doesn't actually withdraw, but simply exchanges CAP->BTC then uses that BTC to buy WDC... from that same exchange. Not being able to remove it to your personal wallet is simply a hinderance. That can be instantly warned, prior to exchange, if the system takes that into consideration. Not everyone "cashes-out", many just keep trading from coin to coin.)
The short solution is to temporarily raise the "confirm acceptance" for the exchange to something crazy like 10,000 confirms for deposits, and stop all withdraws. Then, inform anyone making a trade, that they will not be able to withdraw that coin, only trade for another coin, which can be withdrawn. While any pending deposits will be notified on a similar level, alerting them that pending deposits will not be available for trade, until the fork has found a resolution. Asking them not to deposit, until the fork is over, and alerting them that pending deposits may not come through, and may have to be resent, if they were sent from the wrong fork. (If sent from the wrong fork, the coins would return to the wallet of the sender, once the bad fork disappears.)