Photoshop CC - slow saving .pngs - 4 minutes!

I've used Photoshop for a while and have saved many .pngs at the smallest size option without an issue. It always saved in a reasonable time in the past.  But for the last few days when I've gone to do the same type of projects again the saving time is ridiculous. I timed a couple of saves to be sure and one was 4 minutes 20, the other 4 minutes 30. I tried increasing the memory setting in preferences thinking that might help, but it hasn't. Nothing has changed on my PC, so that's not the cause.

Does anyone know why this is happening. This amount of slow down is just not acceptable when doing projects.