The 'modify walls' menu choice is greyed out when I select the walls of my plan. When I click on a wall, all of the walls are highlighted in purple and arrows appear at each intersection. The plan is not locked.

I am using a MacBook running OS 10.9.1, Sweet Home 3D version 4.3 and Java version 1.6.0_65. I have read the user manual and posts on this topic from 2010 and 2012.

I apologize in advance since I'm probably missing something obvious.

Thanks for any help you can provide!