Don't know if this is the right place to report this, but hoping @wimpy sees this.
I noticed that the file copy window was completely blank showing no info whatsoever during file copy.
File copy still works, but some update to MATE 1.8 or related packages must have caused this behavior.
I believe UM 14.04 is supported to April 2017 so it would be nice with a fix before that. I want MATE 1.8 to "go out with style" like the finest pure GTK2 desktop.