Steps to reproduce:

1. Start Steam
2. Go to Steam→Backup and Restore Games...
3. Choose Backup currently installed programs then click Next
4. Pick any game you want then click Next again
5. Open file dialog with Browse... button and finally click New folder... to open 'Choose directory name' dialog;

Actual results:
Can't enter any characters other than latin(cyrillic, i.e.);

System information:

Processor Information:
    Vendor:  GenuineIntel
    Speed: 2100 Mhz
    4 logical processors
    2 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:
    Ubuntu 12.04.1 LTS (64 bit)
    Kernel Name:  Linux
    Kernel Version:  3.6.3-030603-generic
    X Server vendor:  The X.Org Foundation
    X Server release:  11103000

Video Card:
    Driver:  Intel Open Source Technology Center Mesa DRI Intel(R) Sandybridge Mobile x86/MMX/SSE2

    Driver Version:  3.0 Mesa 9.0
    Desktop Color Depth: 24 bits per pixel
    Monitor Refresh Rate: 60 Hz
    VendorID:  0x8086
    DeviceID:  0x116
    Number of Monitors:  1
    Number of Logical Video Cards:  1
    Primary Display Resolution:  1366 x 768
    Desktop Resolution: 1366 x 768
    Primary Display Size: 10,91" x 6,14"  (12,48" diag)
                                            27,7cm x 15,6cm  (31,7cm diag)
    Primary VRAM Not Detected

Sound card:
    Audio device: 

Memory:
    RAM:  7873 Mb

Miscellaneous:
    UI Language:  English
    LANG:  en_US.UTF-8
    Microphone:  Not set
    Total Hard Disk Space Available:  186467 Mb
    Largest Free Hard Disk Block:  2322 Mb

Installed software:

Recent Failure Reports: