Error with groups on re-opening (#382)

I have groups and when I was creating them everything worked perfectly. I copied my groups for easy editing.

Now I have loaded the file again and all my groups are from the type Unknown (http://gyazo.com/8af1c554fb80d84622ea349819819f37)

I cannot copy anything anymore aswell, I always get this error: http://gyazo.com/9515e29e2aa6821b9fbd5982c00e3317