I personally think the exchanges are investigating some kind of fraud practices, or as someone said, that pac coin has been hacked and the website has been taken over by unknown people... probably the dev of pac has asked cryptopia to lock down the coin till further things get in control. One exchange can go in maintenance mode for this coin, not two.. there is more to what meets the eye.
It is possible.
When a cryptocoin becomes hot and during the upgrade and swap to a new coin, it might invite 51% attacks, causing a short fall in the exchange overall PAC balances.
Actually Cryptopia's DOT coin did suffer from such attacks
DOT stopped scrypt-POW mining and was switched to Ubiq platform last year.
https://www.cryptopia.co.nz/Forum/Thread/1822?postId=9084https://www.cryptopia.co.nz/News Dotcoin(DOT) Coin Swap
Recently there has been a large uptick in coins being affected by 51% attacks, and unfortunately DOT joined this list earlier in the week. We managed to identify and respond to the attack sooner rather than later though the attacker did manage to make an impact on the market. This is the reason DOT has been in maintenance while we tried to determine the best response to the issue. Due to the amount of hash that can readily and easily be thrown around at small networks these days we had to ask ourselves if it still makes sense for DOT to run on its own network as it is clear to us that we cannot afford secure the network ourselves, and that the demand for DOT is not sufficient enough to attract the amount of distributed computing power required to sufficiently secure the network either. We've decided to perform a swap of the DOT blockchain to a WAVES asset, the use case of DOT is not based around mining or proof of work so we don't think anything is lost in moving DOT to a token platform. A final block height will be defined to allow for a swap period of approximately 90 days before the cut off of new blocks being included in the swap. The new token will be created and swapped 1:1 with the old chain with the new asset matching the coin count of the old chain up to the cutoff block height. Cryptopia will also keep a copy of the old blockchain so that old coins prior to the cutoff block height can continue to be swapped. Cryptopia will allow for a full year before the swap process is closed and swaps of coins on the old chain will no longer be accepted. Cutoff Block: 1,200,000 Total DOT at block 1,200,000: 522,500,000 DOT New DOT Asset Total: 522,500,000 DOT If you already have your DOT on Cryptopia then there's nothing further you need to do everything will be swapped automatically, this included all DOT currently in Term Deposits that will remain uninterrupted. If you do not currently have your DOT on Cryptopia and want the swap to happen automatically then you must deposit your DOT to Cryptopia before block 1,200,000. If you fail to swap your DOT before block 1,200,000 you will have to raise a support ticket to get your swap sorted. Cryptopia has covered the DOT that was lost in the 51% attack from their own DOT reserves, so all users will remain completely unaffected by the attack. The final date for swapping your DOT will be 2018-07-01.
Published by: Hex @ 6/29/2017 3:38:11 AM
I hope fix will be done soon. For now i am stuck with my shares to PAC. 
