Custom theme interfering with admin sorting

Hi All,

My site uses a custom theme I developed many years ago, probably during very early v3 of WP (if not earlier).

I recently updated to version 3.9 of WP and the theme generally works well, but sorting my posts doesn’t seem to work. This is appearing in 2 places:

– On the front-end no matter how I choose to order and orderby the posts in my theme, they always display with the oldest post first
– On the back-end, I can’t sort by any columns in the admin interface (date, title, etc.). I click the column heading to sort and nothing happens

I’ve tried disabling all plugins, but that did nothing.

So then I just activated the 2014 theme and the problem went away, leading me to believe there’s something wrong with my theme. I have no idea what though, it’s such a simple and basic theme.

Anyone know what could cause this issue? Thanks in advance.