This article outlines the steps on how to fix Cascading Lookup Plus Field Type "An entry with the same key already exists" error.
Example: There is an error when adding a cascading Lookup column as a new column in SharePoint 2010 template (See image below)
Product & Version
KWizCom Cascading Lookup Plus Field Type Standard Evaluation 3.x.xx for SharePoint 2007
KWizCom Cascading Lookup Plus Field Type Standard Evaluation 13.x.xx for SharePoint 2010
Please check "All Site Content" see if there are two lists with the same name. This error will be fixed after removing the duplicate one.
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