If masquerade's table already exists (which it might for a variety of reasons), turning the module on produces
DatabaseSchemaObjectExistsException: Table <em class="placeholder">masquerade</em> already exists. in DatabaseSchema->createTable() (line 652 of C:\inetpub\wwwroot\RCS\includes\database\schema.inc).
My particular scenario is that I backup the data from my production server - which does not have masquerade installed - and restore it to my development server - which does. I thought it might help if I disabled masquerade before restoring, but it does not. I can work around this by making sure masquerade is disabled and going into the db and removing two tables (masquerade*) - but I have to remember how to use mysql to do this :).