I've experienced the same issue. I spend 1/2 hr doing a label, then I try to save it and get an error. Then if you try to pull it up you get this error. So once I get the error, I realize that I just lost that work - the most I can do at that point is make a screenshot before I close and try recreating it. I have wasted a lot of time having to redo labels because of this issue. I've tried pulling it up a different way and that doesn't work either. If anyone has a solution please let me know.
Side note...my experience is that all of the Roxio v8 suite of products suck, Big time. I've had problems with every single product I've used in this version - crashes, data not being saved, losing info, Tons of features not working, etc. I've worked for software companies so I know the norm is to have a few bugs, but this is one of the Worst software products I've ever used in my life. Roxio support also is minimal and unhelpful if and when they even respond, and they leave the users to figure stuff out on their own. It amazes me that such a big name company can do business like this.