Blog copying plugins suddenly do not work (but have worked fine in the past for 50+ blogs)

Our multisite installation has worked beautifully until today. Suddenly ( and we do not know why) we cannot get any blog copier plugin like "Blog Copier" or "New Blog Templates" to recreate an existing blog. Seriously, this worked fine until today and we have about 50 active blogs on this site. Has anyone experienced this, and is there a fix? Are we mysteriously missing a database table or ??? Totally at a loss. Thanks! Valerie
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