What kind of error occurs? What do users experience? Can you access the database using tools and what if you get it back under the 4GB / 10GB limit?
You might see an error like this:
CREATE DATABASE or ALTER DATABASE failed because the resulting cumulative database size would exceed your licensed limit of 4096 MB per database.
Or this:
Could not allocate space for object 'dbo.buyspace'.'PK__buyspace__4B5BD7F83A81B327' in database 'WAYTOOBIG' because the 'PRIMARY' filegroup is full. Create disk space by deleting unneeded files, dropping objects in the filegroup, adding additional files to the filegroup, or setting autogrowth on for existing files in the filegroup.
That's from our error log.