Big picture: http://i.imgur.com/uB3WF5D.png
Edit1: To get rid of it, I repeatedly press Escape until bothe the error message and the Side WRA windows are closed. Note that the scenario is still smoothly running "on the background".
To reproduce, start the scen, modify the Side WRA for a few weapons and see the error message.
Edit2: It have been observed after a complete restart of the game too, though it seems that I was able to input more changes before it happened.
Edit3: another way, simpler, to reproduce: just load teh save, don't actually start the scen, go on the Side Doctrine & ROE window, WRA tab, click on the + sign to expand the options for the KAB-1500Kr-Pr TV/Eo (last weapon at the bottom), then scroll down the list.
Version: Command v.1.07 Release Candidate 1 (Build 673).
DxDiag: http://warfiles.org/divers/JanDxDiag160215.txt
Saves attached.