Sounds like you have a 3D element that has errors in it. Can you generate the project in the 3D window?
In your work environment turn on the error report, even just a short one so you get error messages. That error message might help you narrow down which element(s) are causing problems.
Otherwise using the heavy marquee select one half of the project and then the other half to identify where the bad element is. In the half that has error reports, select half of that etc until you can identify and fix the object causing the problem.
When you generate a section or elevation, if the problem object is within the range of the s/e then it will be slow to generate and/or cause error messages.
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"