The very, very odd time the Steam client is open, I will see the graphic of a clear, narrow box on top of any application I have running in front of the Steam client.

Here I have a browser open in front of the Steam client.

What's more, if I click on the box, it brings the Steam client to the front, and highlights whatever item my cursor was on top of at the moment (a game title, a link, etc).

I can see the box outline on top of the Steam client and on the desktop background, too.

Thank you.

System Information:

Processor Information:
Vendor: AuthenticAMD
CPU Family: 0x10
CPU Model: 0x5
CPU Stepping: 0x3
CPU Type: 0x0
Speed: 3100 Mhz
4 logical processors
4 physical processors
HyperThreading: Unsupported
FCMOV: Supported
SSE2: Supported
SSE3: Supported
SSSE3: Unsupported
SSE4a: Supported
SSE41: Unsupported
SSE42: Unsupported

Network Information:
Network Speed:

Operating System Version:
Ubuntu 12.04.4 LTS (64 bit)
Kernel Name: Linux
Kernel Version: 3.8.0-39-generic
X Server Vendor: The X.Org Foundation
X Server Release: 11303000
X Window Manager: Compiz
Steam Runtime Version: steam-runtime-release_2014-04-15

Video Card:
Driver: ATI Technologies Inc. AMD Radeon HD 6700 Series

Driver Version:  4.3.12682 Compatibility Profile Context 12.104
OpenGL Version: 4.3
Desktop Color Depth: 24 bits per pixel
Monitor Refresh Rate: 60 Hz
VendorID:  0x1002
DeviceID:  0x673e
Number of Monitors:  1
Number of Logical Video Cards:  1
Primary Display Resolution:  1920 x 1080
Desktop Resolution: 1920 x 1080
Primary Display Size: 23.62" x 13.39"  (27.13" diag)
                                        60.0cm x 34.0cm  (68.9cm diag)
Primary VRAM Not Detected

Sound card:
Audio device: VIA VT1708S

Memory:
RAM: 7984 Mb

Miscellaneous:
UI Language: English
LANG: en_CA.UTF-8
Microphone: Not set
Total Hard Disk Space Available: 232570 Mb
Largest Free Hard Disk Block: 114934 Mb

Installed software:

Recent Failure Reports: