Sounds like a preset got applied automatically during the import.
Pick on of the b/w images, view its edit history in the Develop module.
Check your import settings in the right pane of the import dialog.
I have a Mac and all of my software is up to date. For some reason, this just happened to me today. Both LR and CC2015 "turned" my pictures to a B&W rendition. Still have no idea why as there are no presets being applied during import. The way I fixed it though was to go into the Develop module and click on zeroed (Zeroed preset is found on the left hand side under Lightroom General Presets. I had to do that for each picture.) That fixed the problem, and I am able to edit in LR and CC2015 as usual.
The pictures did open up normally with other programs such as CaptureNX2, Preview, Aperture, etc. Fortunately I had only imported 15 pictures. It I had imported 300 or so, it would have been a nightmare.
Going to experiment with another camera and another set of pictures to see if the same thing happens. Will update later.
Found this on another website - Change the Develop Import Settings - To change the defaults back, select one of the B&W files in the Develop module, the use the menu bar: Develop>Set Default Settings>Restore Adobe Default Settings. That should fix things for subsequent imports. So far - it works!