This is rather odd...

[#1]

I have a two monitor setup and it works extremely well for me. I often have certain things being viewed on the largest (right) monitor and the remainder on the left. Sometimes I drag from one to the other with no issues, till now.
Usually I have MyPhoneExplorer on the right monitor but this evening I moved it to the second one so I could drag files from a couple of windows already opened there. I was viewing the Files section in MPE but noticed that no matter what folder I clicked in the left-hand display within MPE the right-hand part wouldn't change to reflect the contents of the chosen folder. Moving the MPE window back onto the first monitor and all works again as expected.
Has anyone seen anything like this happen?

[#2]

your using w7 with amd gfx card and  extended desktop ?
trying to run 2 monitors in extended desktop is what lead to my gfx card failing a day out of warranty, I think amd borked the driver update and it ended up killing the card .....

[#3]

I've noticed this sometimes happens when the DVI  connectors come lose

[#4]

DVI's at both ends are securely inserted.
As it's not a major issue I'm not unduly concerned but would have been nice to know why this is happening.

[#5]

Quote from: Mav

... I'm not unduly concerned but would have been nice to know why this is happening.

I haven't got a solution for you, but it got me thinking that maybe the Window in question somehow had an affinity to a particular display.  I Googled 'set window display affinity' and would you believe it, there is actually a function called 'SetWindowDisplayAffinity' !!!
Perhaps something for you to investigate.

[#6]

Thanks for that, RobPN.
A little Google research and it seems that the SetWindowDisplayAffinity function is for preventing screen shots of the window from being taken. I was able to take screenshots from both monitors so not sure if that is the answer.