O problema é explicado na documentação oficial debian: Problemas de tempo de execução do Steam .
Steam ships with its own versions of some libraries (the "Steam Runtime") in an attempt to emulate the Ubuntu 12.04 environment in later versions of Ubuntu.
However, some core libraries included in the Steam Runtime will often conflict with the newer versions of other libraries included in Debian (such as drivers, and specifically the open-source ATI driver).
Para resolver o problema:
remove offending files from Steam Runtime
# rm ~/.local/share/Steam/ubuntu12_32/steam-runtime/i386/usr/lib/i386-linux-gnu/libstdc++.so.6
# rm ~/.local/share/Steam/ubuntu12_32/steam-runtime/i386/lib/i386-linux-gnu/libgcc_s.so.1
# rm ~/.local/share/Steam/ubuntu12_32/steam-runtime/amd64/lib/x86_64-linux-gnu/libgcc_s.so.1
# rm ~/.local/share/Steam/ubuntu12_32/steam-runtime/amd64/usr/lib/x86_64-linux-gnu/libstdc++.so.6
# rm ~/.local/share/Steam/ubuntu12_32/steam-runtime/i386/usr/lib/i386-linux-gnu/libxcb.so.1
# rm ~/.local/share/Steam/ubuntu12_32/steam-runtime/i386/lib/i386-linux-gnu/libgpg-error.so.0
Reinicie seu sistema.