A managed solution cannot overwrite a {0} component on the target system that has an unmanaged base instance. The most likely ...

A managed solution cannot overwrite a {0} component on the target system that has an unmanaged base instance.  The most likely scenario for this error is that an unmanaged solution has installed a new unmanaged {0} component on the target system, and now a managed solution from the same publisher is trying to install that same {0} component as managed.  This will cause an invalid layering of solutions on the target system and is not allowed.