I can't recall having seen this. Perhaps there is a setting in the Work Environment. I know there is (or was) a setting for the palette to move to a default location or follow the cursor (the pest palette setting). Perhaps changing (or toggling)this would help.
Try doing a new and reset.
While opening a new file, File>New hold the alt/opt key down and it will say New and Reset. This won't hurt any open files, although I'd close them. This will restore the default settings.
MacBook Pro Retina, 15-inch Yosemite 2.8 GHz Intel Core i7 16 GB 1600 MHz DDR3
Mac OSX 10.11.1
"Implementing Successful Building Information Modeling"