What version of PandaBank were you running?  Your Pandacoins should be safe on the blockchain but you need to have your Private key safe to prove they are yours, the easiest and best way to protect your private key is to have a copy of your wallet.dat in a safe place. Start by backing up your wallet.dat, are you familiar with where your Pandacoin Data folder is?  On mac your Pandacoin data folder is in ~/Library/Application\ Support/Pandacoin. It is a good idea to always have a backup of your wallet, especially if you encounter a problem. The older version of PandaBank 3.0.2 can have difficulty with it's default hybrid mode which will probably require you to reset your blockchain and resync.  

You can do this after you have backed up your wallet.dat to be safe,  then delete all the files/sub folder in your Pandacoin data folder except wallet.dat and peers.dat and Pandacoin.conf if you have it.  You may just have trouble with finding nodes to connect too, having valid nodes in a Pandacoin.conf can help but the latest PandaBank v3.0.5.6 has built in valid nodes so a Pandacoin.conf is not required. When you restart PandaBank it will recreate the deleted files it needs and start to sync again.  If you are in Hybrid mode, it is recommended you switch to classic mode right away.  It would be helpful to have some feedback on our recent updated PandaBank for mac, please consider trying this procedure with our latest PandaBank QT 3.0.5.6 standalone for MacOS. You can download the latest here http://cryptodepot.org/downloads/    Use right click then open so you can allow it to run.