We have a field in one of our modules which we use to trigger a mass update to over 3k records on every week.

We do this simply to update some formulas involved there. 

Suddenly this seems to have stopped working. The "Ok, Proceed" button isn't clickable. This is happening across multiple browsers. Is it just us that's having this?

The button can't be clicked because it's grayed out - this has never happened. It's also happening with another unrelated module so it's 100% not because something in the module itself was changed.