When exporting geodatabase annotation to coverage annotation the following error may occur:
Invalid coverage type annotation.<name.<name>
Where <name>.<name> can be any text string with a period in it, i.e. parcels.anno.
This error is caused by periods in the subclass name field in the Geodatabase to Coverage dialog box. Periods and non-alphanumeric characters are not supported for coverage annotation, except for underscores.