I am having a problem in creating new signatures in Signature Editor in ERDAS 2014. Whenever I click on the icon (i.e., after selecting the aoi), it shows an error which says "unable to open associated image: Image association may be edited with Edit menu (Image Association...)". After I had set the associated image from the edit menu of the Signature Editor and tried to create new signature, it displayed "Viewer image does not match associated image for signature set. Image association may be edited with Edit menu (Image Association...)". PLEASE HELP!!!
Check your folder name which contain your satellite imagery. Is it too long or is it contain spaces, like for example "D:\This is the folder name 123"? This kind of folder could raises problems in ERDAS.
I face the same problem, and resolve it just by move my image into the simple folder, such as "D:\Image". Just set this folder as your default data folder via File > Preferences; and try the same procedure for the AOI creation and adds it to signature editor.