I'm putting text into boxes on master based pages. Was working fine until suddenly, two of my master based pages won't let me select inside the text box. I can't even select the text box. I've tried everything I can think of. I've deleted the page and tried it over again, I've hit Shift+ click, shift+ctrl+click etc. I can't figure it out!
Nevermind. I got it.
I know you got it sorted, but since you are calling them text "boxes" suggests you may be a former (or current) Quark user. Quark needs master text boxes if you want to flow text into a document and create pages at the same time, but InDesign does not. There are some scenarios where using master text frames can be helpful, but in most cases you are better off creating the text frames on the document pages.
I would also recommend not to use master text frames in InDesign, exceptions are frames for page number, running header or primary text frames in a layout for books or similar layout, and in some rare exceptions but never use it as a general tool as you would do it in Quark Xpress.