Red wall around window, what can i do ?

[ian 32]

hi guys I have a nice simple model house I have in archicad, exported to 3ds and brought it into netfabb.

did a standard repair on the model and found the model almost ready to go. Just spotted a wall high lighted red around a window and also two yellow lines around the corner wall.

what do those two symbols mean and how can i make this wall around the window correct.

Also when im chatting about netfabb, when i have an opening and make a new object, resize it and move it to close the whole, how can i combine my original model with the new element, so that when i test or repair the combined model, the repair otion will effect it as 1 entity.

thanks guys.

Ian