I'm having the same problem in SW 2014 x64 SP 2, but I'm doing some commands like Shell and Fillet in a solid model.
I have a Dell T7500, Win 7, NVidia Quadro 2000.
My doesn't always do it, but it seems to do it always with certain commands, such as Shell, when there is an error. My part is complex and it has to do a lot of calculating to do the Shell.
I've been hitting the check mark repeatedly very fast and it subliminally tells me the error message.
I've only had that happen with design table errors. I have no idea why it happens, but my only suggestion is to keep creating the error and try to do a print screen right when it pops up. If you are lucky you'll catch it and be able to paste into paint and see the message.
When this happens I take a video of the screen (phone camera could be good enough or use a video screen-grab program) and can usually catch the message as it flashes up for a frame or two.