This check box?

Yes, it is.

I think I just ran into this issue with making a purchase with the Linux client, I checked the box "I currently live in the country selected above" but it kept asking me to verify my country. I believe that the "checked" and "unchecked" icon is actually reversed, so the webpage is correct but the icons are not. The same problem occurs on the next page, as I also had to uncheck agreeing to the subscriber agreement to complete my purchase.

Other reports include confirmation of purchase and adding new methods of purchasing.

Website works fine for me and checkboxes in Linux (Firefox 21.0).
Though, when using the client, they're reversed. I have to disagree the EULA to sell stuff on the market.

Upside it that I don't have to do click stuff when I need to sell or buy as it is unchecked per default.

Same problem here.

I have to uncheck the Country box to continue the purchase and also I have to uncheck the Steam Agreement Box to continue.

System is a current Funtoo (Gentoo) Box.

Also seeing this issue

I Just double purchased $50 in wallet funds because of these inverted checkboxes and error messages that mean nothing. Is there a way to drop an updated .so for webkit/chrome somewhere?

I just had the same problem while purchasing a game (i.e. the order would not go through if the "I agree to the terms of Steam Subscriber ..." checkbox appears to be ticked).

Processor Information:
    Vendor:  GenuineIntel
    Speed: 2200 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 13.04 (64 bit)
    Kernel Name:  Linux
    Kernel Version:  3.8.0-26-generic
    X Server Vendor:  The X.Org Foundation
    X Server Release:  11304000
    X Window Manager:  KWin
    Steam Runtime Version:  steam-runtime-release-i386_2013-06-28

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

    Driver Version:  3.0 Mesa 9.2.0-devel
    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: 12.17" x 6.85"  (13.94" diag)
                                            30.9cm x 17.4cm  (35.4cm diag)
    Primary VRAM Not Detected

Sound card:
    Audio device: Intel CougarPoint HDMI

Memory:
    RAM:  5917 Mb

Miscellaneous:
    UI Language:  English
    LANG:  en_US.UTF-8
    Microphone:  Not set
    Total Hard Disk Space Available:  487123 Mb
    Largest Free Hard Disk Block:  282186 Mb

Here's a screenshot of the order NOT going through:

This way it DID:

Same issue here.

Same in Friend Activity Settings. All of the following options are enabled:

The "Subscribe to discussion" checkbox in the community discussion threads is this way too.

And it does!