I have the same exact issue ... I had to pull up an image in ENVI Classic to create the annotation and save it as a .ann file - ENVI 5 only saves annotation as .anz and the 3D Surface View tool only reads .ann format annotation (flight line) ... the lesson in the Exploring ENVI manual (Chapter 4: Vegetation Analysis, Exercise 10, Step 8, page 65) just doesn't work and needs to be rewritten - it refers to a 3-window view to draw the annotation, but as you work the exercise, there is NO 3-window view... Also in that lesson (same chapter, Exercise 1, step 1) calls for the tool "Calibrate Landsat" which is not available in the Student-licensed version of ENVI 5. Why put that in a student manual if the student can't access it ?!?! ... luckily it's in the ENVI Classic version so I was able to work around that (too).

Same issue here too... I just spent an hour creating cutline polygon annotations and can't use them as the mosaic tool only reads *.ann. Back to Classic again (as usual...)