Confirmed with Opera 8.54 on Mac OS X 10.5
Confirmed with a local copy of the login webpage that removing the jQuery imports from the HTML resolves the problem.
With jQuery enabled, the following JS error is presented:
Event thread: load
Error:
name: TypeError
message: Statement on line 759: Could not convert undefined or null to object
Backtrace:
Line 759 of linked script http://en.wikipedia.org/skins-1.5/common/mwsuggest.js?227x if (element.addEventListener) else Line 777 of linked script http://en.wikipedia.org/skins-1.5/common/mwsuggest.js?227x os_hookEvent(document.getElementById(formname), "submit", function (event)
{
return os_eventOnsubmit(event);
}
);
Line 862 of linked script http://en.wikipedia.org/skins-1.5/common/mwsuggest.js?227x os_initHandlers(id, form, element); At unknown location [statement source code not available]
Version: unspecified
Severity: critical
URL: http://en.wikipedia.org/wiki/Wikipedia:Village_pump_(technical)#Login_problem