Recently, I've been having problems getting Frequency to run when I want to specify an upper bound, say 500 Hz, instead of a fixed number of frequencies. I'm using Solidworks Premium for sine-on-random vibration.  I've been running this type of analysis for years, but never had this problem before.  I know that I need the iterative solver, and I've tried everything for explicitly specifying the iterative solver, but I always get this error:

Calculation of frequencies up to an upper bound is only available with the Iterative Solver.

I've also tried deleting all the results files, but still the same problem. I see that Go Engineer at http://files.goengineer.com/docs/support/Simulation_Choosing_Solver.pdf has listed situations where the iterative solver will be turned off and the direct solver used instead, but those conditions don't apply to me.  I'm wondering if there's a bug since I've been running these types of simulations for years now and this error seems to have happened after the install to 2015...

Thanks for any help.

Dave