Turn off auto import. You may have a corrupt file.
I'd guess it is this, if it happens with multiple machines. I agree with Jim. Turn off Auto-Import and see if the issue disappears.
Try switching the internal browser engine from "chromium" to "internet explorer".
If you manually switched it to Chromium in the past, maybe, but this will generally not lead to crashes or lockups when just playing media. Besides, Chromium is not the default option, so I wouldn't jump there first. The Chromium browser plugin has also gotten much better behaved over the last year or so...
I'm skeptical about this, but I suppose worth trying if nothing else works. It should only be done in isolation, though, or else you aren't doing a proper test.