Doesn't show month when scheduling post

Well, I’ve been setting up a website for quite some time now and I’ve just ran into quite an odd problem. At least for my taste. As I haven’t had the need for this function before, I’m affraid it slipped through earlier testing phases so I’m not sure when or where it went wrong.

When I try to schedule a post for a later date, let’s say tomorrow for the sake of the argument, I get a dropdown box where I’m supposed to select the month. However, this dropdown menu is filled with 12 empty fields. They still actually function properly, but they just don’t show any text / names of months.

Now my first guess is that the problem lies in locale.php, seeing as how I defined the translated month names, that I use as the timestamp, in there.

I’ve pasted all the month-related info from locale.php below, and here’s a screenshot of what happens in wp-admin:

https://img191.imageshack.us/i/publish.jpg/

Can anyone point me in the right direction? Having it not display names is really confusing.

// The Months
		$this->month['01'] = /* translators: month name */ __('januari');
		$this->month['02'] = /* translators: month name */ __('februari');
		$this->month['03'] = /* translators: month name */ __('maart');
		$this->month['04'] = /* translators: month name */ __('april');
		$this->month['05'] = /* translators: month name */ __('mei');
		$this->month['06'] = /* translators: month name */ __('juni');
		$this->month['07'] = /* translators: month name */ __('juli');
		$this->month['08'] = /* translators: month name */ __('augustus');
		$this->month['09'] = /* translators: month name */ __('september');
		$this->month['10'] = /* translators: month name */ __('oktober');
		$this->month['11'] = /* translators: month name */ __('november');
		$this->month['12'] = /* translators: month name */ __('december');

		// Abbreviations for each month. Uses the same hack as above to get around the
		// 'May' duplication.
		$this->month_abbrev[__('January')] = /* translators: three-letter abbreviation of the month */ __('Jan_January_abbreviation');
		$this->month_abbrev[__('February')] = /* translators: three-letter abbreviation of the month */ __('Feb_February_abbreviation');
		$this->month_abbrev[__('March')] = /* translators: three-letter abbreviation of the month */ __('Mar_March_abbreviation');
		$this->month_abbrev[__('April')] = /* translators: three-letter abbreviation of the month */ __('Apr_April_abbreviation');
		$this->month_abbrev[__('May')] = /* translators: three-letter abbreviation of the month */ __('May_May_abbreviation');
		$this->month_abbrev[__('June')] = /* translators: three-letter abbreviation of the month */ __('Jun_June_abbreviation');
		$this->month_abbrev[__('July')] = /* translators: three-letter abbreviation of the month */ __('Jul_July_abbreviation');
		$this->month_abbrev[__('August')] = /* translators: three-letter abbreviation of the month */ __('Aug_August_abbreviation');
		$this->month_abbrev[__('September')] = /* translators: three-letter abbreviation of the month */ __('Sep_September_abbreviation');
		$this->month_abbrev[__('October')] = /* translators: three-letter abbreviation of the month */ __('Oct_October_abbreviation');
		$this->month_abbrev[__('November')] = /* translators: three-letter abbreviation of the month */ __('Nov_November_abbreviation');
		$this->month_abbrev[__('December')] = /* translators: three-letter abbreviation of the month */ __('Dec_December_abbreviation');

EDIT:

I have tried changing the “Jan_January_abbreviation” to “Jan” and so on, but that didn’t change anything.