Steps to reproduce:
Bug only happens if "Save an uncompressed copy outside of Ste..." is selected.
Go to steam settings, randomly change tabs couple of times (FRIENTS,IN-GAME,VOICE etc...) OR change some options and then click OK. After Settings dialog closes, other bugged dialog opens with name "Select external screenshots folder". Dialog is unresponsive and I need to right click it on taskbar and click Close to get rid of it.

Bug also only happens when OK is clicked, by clicking CANCEL bug never happens.

If I open "Select external screenshots folder" dialog under "IN-GAME" tab in Settings it works just fine.

There is also minor text bug in "Save an uncompressed copy outside of Ste..." string.

System information:
Processor Information:
Vendor: GenuineIntel
Speed: 4301 Mhz
8 logical processors
4 physical processors
HyperThreading: Supported
FCMOV: Supported
SSE2: Supported
SSE3: Supported
SSSE3: Supported
SSE4a: Unsupported
SSE41: Supported
SSE42: Supported

Network Information:
Network Speed:

Operating System Version:
"Gentoo Base System release 2.1" (64 bit)
Kernel Name: Linux
Kernel Version: 3.6.11-gentoo
X Server vendor: The X.Org Foundation
X Server release: 11302000

Video Card:
Driver: NVIDIA Corporation GeForce GTX 660 Ti/PCIe/SSE2

Driver Version:  4.3.0 NVIDIA 313.18
Desktop Color Depth: 24 bits per pixel
Monitor Refresh Rate: 60 Hz
VendorID:  0x10de
DeviceID:  0x1183
Number of Monitors:  1
Number of Video Cards Not Detected
Primary Display Resolution:  1920 x 1080
Desktop Resolution: 1920 x 1080
Primary Display Size: 20.91" x 11.77"  (23.98" diag)
                                        53.1cm x 29.9cm  (60.9cm diag)
Primary Bus: PCI Express 16x
Primary VRAM: 2048 MB
Supported MSAA Modes:  2x 4x 8x 16x 

Sound card:
Audio device:

Memory:
RAM: 32098 Mb

Miscellaneous:
UI Language: English
LANG: none
Microphone: Not set
Total Hard Disk Space Available: 476939 Mb
Largest Free Hard Disk Block: 439535 Mb

Installed software:

Recent Failure Reports: