From what I have read, there shouldn't actually be new lines in the title attribute. BUT if you do want to try, use " " which is a carriage return. In firefox, the return is converted to a space, but in IE you will see a line break in the tool tip (which I think is incorrect behaviour).

Hope that helps...

Thanks, I tried that, and you're right: In FireFox it's just a space.
There should be a better solution, but I guess I'll just not show any title but open a small message box instead.