My company is fairly new to using Arbortext Editor and we don't have scripts attached to the editor yet. This is happening to a few people. Basically, after awhile, Arbortext Editor will let you select text or an element, but after one second it forgets about the selection. We are using Arbortext Editor 6.0M running on Windows 7. We do have a few customizations, but they are utilities you click on to activate.
Also, we are using Arbortext Editor with SDL LiveContent Architect.