"Down for Maintenance" only on admin/orders.php?

I've been trying to add a field to the checkout-shipping page and display it in the list on the admin/orders.php page. I followed the gist of the instructions in this post and got it working perfectly locally. When I push the changes to the live server, however, I get a "down for maintenance" message on the admin/orders.php page only. The front end of the site works fine, and the new field gets saved in the database when an order is placed. The rest of the admin works fine, just not orders.php. I've checked ZC's error log and the hosting account's PHP error log, but neither contains recent errors. I'm wondering how else I can troubleshoot where this behavior is originating? That's where I'm stuck -- with nothing showing up in logs, I don't know how to tell what's going wrong.

I'm using a BitBucket git repo as origin for both my local and live repos. The files are identical between local and live (except for configure.php, .htaccess, and caches and logs). I even copied the live database down to test locally and it works with my updated files. PHP version is 5.4 both locally and live. Any tips on how to hunt for an error that causes a "down for maintenance" message on only admin/orders.php? I've been digging through this so long I'm not sure what to try next.

The exact maintenance message is "We're down for maintenance, but we'll be back up soon. Please check back!" This appears as the only content on a white page, with no header or footer. The url of this page is admin/orders.php -- it's not the standard nddbc.html or anything. It persists for a couple of hours even after I reset my changes. Also, when I search the site files for the above maintenance string, I come up empty.

Thanks in advance for any light anyone can shed.

Well, this was odd. Turns out my code was fine, but the permissions for orders.php were 664 when they should have been 644. That caused the server to throw a 500 error, but the 500 error page had been set up to display a generic message without mentioning the fact that it was a 500 error. Once I figured that out, I took a closer look at orders.php and noticed the permissions problem.

What's weird is that I'm using git to deploy, so the files should mirror my local copy exactly, and my local copy had the correct permissions. I'm chalking this up to a glitch in the matrix.

ecclescake:

What's weird is that I'm using git to deploy, so the files should mirror my local copy exactly, and my local copy had the correct permissions.Out-of-the-box git doesn't retain file permissions.