Selecting of checkboxes different under 1.4.4 and 1.5 or above

[LaySoft]

I have two checkboxes:

<input type="checkbox" id="x"/> <input type="checkbox" id="x:y"/>

under jQuery 1.4.4

$(':checkbox[id^{=x:]').attr('checked','checked');}

and

$(':checkbox[id^{=x\:]').attr('checked','checked');}

checks only second checkbox.

But under jQuery 1.5 and 1.5.1 checks both checkboxes.

[addyosmani]

Duplicate of #8410.