Regarding this error, please go through the following steps: (Make sure you have full database backup prior running these scripts)
1. In SQL Query Analyzer you will want to find the PlanID # by running the following query and entering the Plan Number in place of the XXXXX, the query will pull up the PlanID# for the Plan that is causing the error.select * from RPPlan where PlanNumber = 'XXXXX'
2. Click Execute
3. The results will give you the PlanID #. Please copy and paste the PlanID number into the script in place of the XXXXXXXXXXXXXXXXXXXXX
4. Insert the results and click on Execute.
5. Log out of Vision and back into Planning and you will then be able to get back into the Plans.
Solution above based on Deltek Support Case
Case No.170417-000645
Product: Vision / Resource PlanningCreated04/17/2017 04:06 PM
Updated: 04/19/2017 07:47 PM
Status: Closed
Severity Level: S3-Elevated
Issue Type: Application
Verif. Version Using: 7.6
Subject:V76 CU08 Cannot Open Plan - B1240.01 - An item with the same key has already been added.