Why doesn't the transparency of Hangouts icons work in Windows 7?

Question

Windows

I can’t understand at all why transparency in Google Hangouts does not work on one of the machines.
The cars are the same - Windows 7, x64, Aero on, Chrome 39.0.2171.95 m.
But in one case there is transparency:

And in the second - no:

Why does it happen this way and how to fix it?
PS:
- reinstalling, restarting the application didn't help
- reinstalling the whole temple didn't help.