Corrupt font perhaps?
Perhaps -- docs in question have a mix of three families (Myriad - stock CC install, Interstate and ARS Maquette, all OT, all purchased separately, so we have three people using three different file sets), and the behavior is noted when the inline style contains all three.
The resolution varies - today I applied a different style to wider area (before and after the problem spot), then went in a applied the correct styles and not that section is 'fixed' (but the process doesn't always work - it took about 15 crashes to get this one kink worked out). Next time I encounter it, I will do a global replace to see if I can recreate the problem.
Is this one file or all files? If just one, try exporting to IDML and reopening that.