Hey Michael, This error means an ArcGIS Server process has your bundle or index locked and cannot delete it to replace it. This happens in all environments multi or single so do not spend anymore time trying to figure it out. We spent 6 months working on the issue with ESRI support who were convinced it was an enronmental issue only to find this post with other users describing the same issue in the 10.2 release. Restart your ArcGIS Server and attempt to rerun your process and the bundles should create. Try to keep all load off the server if this is not an option, try to resort to building the cache in another service, another server and then move the cache as David and others describe above. Thanks Ronnie
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