ArchiveManager services are generating a SQL login error.
When checking the Database, SQL generates the error "Database ArchiveManager cannot be opened due to inaccessible files or insufficient memory or disk space" Error 945.
Microsoft say Error 945 is returned when the database is marked IsShutdown. This occurs when a database cannot be recovered due to missing files, or some other resource error that usually can be corrected easily.
There are several workarounds for this issue.
In SQL 2005, simply take the Database offline and put it back online.
If the first workaround didn't help, Please see this Microsoft article.