MBP freezes when retina display plugged off

My Macbook Pro freezes almost every time I plug off DP connected DELL UP2414Q Display. I had to hold the power for reboot.

It happened after 10.10.3 update, before it was all OK.

I also run Parallels virtualization software, may it is related.

Do you have an idea for fix before Apple does something in future updates?

Thanks

Denis

mid 2014 15" model

NVIDIA GeForce GT 750M 2048 MB