[BUG]Steam GUI hangs on dual monitor separate X screens

[Wisetrem]

Steam GUI hangs soon after start with Steam process consumes 100% CPU core time.
I seems like process continues to work with no output errors and GUI updates some times, but there is no reaction for the user's moves.

There is no problem like that if I switch to one X screen.

Gentoo amd64, KDE, nvidia-drivers 334.16.

Has anyone encountered something like this or has a solution?