Xmage, Client does not want to Run, as the Card Repository broken or error

If you experience the Card db or repository failure, then simply

Make sure you are in the Mage.Client dir 

$ pwd 

mage/Mage.Client

$ rm -rf db

And then re-run the client,

$ mvn exec:java -Dexec.mainClass="mage.client.MageFrame"

Hope it helps ^^