I HAVE INSTALLED THE DEVELOPMENT VERSION… but same problem…
Yes, for me (on my host) it sound like a memory failure. I can (sometimes, not everytimes) see "try to allocate some xxxxxx bytes…" on the bottom right of the Titles/Metas page, hover the "Last news of Yoast" section.
I have a 48Mo Ram plan.
1- I've upgraded from 1.2.1 to 1.2.5
2- > Failure
3- Downgrade to 1.2.4 > fail
4- Downgrade to 1.2.3 > fail
5- Downgrade to 1.2.2 > fail
6- Downgrade to 1.2.1 > fail
7- Upgrade to DEV version > fail
But… damn… it was resolved when I desactivate BackWPup, yesterday, and now, I also have to desactivate BackWPup AND Subscribe2 to access to Tit/Met page.
Otherwise, for the moment, even if the Tit/Met page is hover, that doesn't break my Titles & Desc on front end.
Not sure, but this need a huge fix, as it sound like a sever memory burst… I don't know…, but it look like an emergency (keeping pressure on Joost ;-D )
(BTW, does anyone know a nice but lightweight plugin for Subscribe2 replacement? This is not my first memory orgy with S2…)