I’m really sorry for the symbol trouble here. Unfortunately, I don’t have a suggestion on how to get this to work at present. When you import the new set of symbols, none of them will be linked up to your project, and that’s why they break.
This is some that will become possible with our new Balsamiq Cloud web application. Since both Balsamiq Cloud and Mockups 3 for Desktop use BMPRs, you won’t need to export and import, which will keep the symbol library links intact.
If you’d like, I’d be happy to invite you to the Balsamiq Cloud Beta, so that you can see if that works better for you. Just let me know.
Otherwise, keep an eye on http://blog.balsamiq.com/. That’s where we will announce its official release!
I’m sorry again for the trouble here. It shouldn’t be a problem for much longer!