Actually, the FIRST thing to do is to contact support at SKM. Call, complain, raise a fuss. They can't fix what they don't know about!
[And they won't fix what peopl;e don't complain about]
{And then THEY will tell you to do the Cleanup ScoptPET talks about
}They RARELY have me do the regdel for this sort of issue.
If you are expired however.....
I would suggest that FIRST you do a backup. Then open the backup project and see if you still have the issue with the oneline.
If you do, then, close the project, and then run the database utility. [From the Project Menu, it is not available when the database is open].
Click on all of the box items, and tell it ok.
Then, after it is done, you can run it though a validation. [Ctrl Shift while you open the project name]
WIth big projects, lots of busses and scenarios, it does take some time. I have never had it take8 hrs plus though. 2-3 hours yes easially.
With small projects however you won't have time to finish a coffee.