A couple of possible fixes. First, undock the pages palette.
There should be a line separating the Master pages from the layout pages. See if that has gotten moved to right up under the "pages" tab. If it has, just drag it down the same way you would a guide line and your masters should be back on top.
If that doesn't work, on the upper right corner there's a tiny little circle with a triangle on its side. Click on that and see if any of that helps. The Show/Hide master button seems to just work on the layout. Check the Palette options menu and see if that helps.
If none of that works, you'll need to trash the preferences files. Something that always needs to be done somewhere along the way with Adobe programs.
Instructions: These are supposed to work in CS3, They don't in CS2. I do appreciate that Adobe is making it easier to find and trash them.
See the "Set defaults" topic for info on restoring preference settings. Here's what it says in a nutshell:
(Windows) Start InDesign, and then press Shift+Ctrl+Alt. Click Yes when asked if you want to delete preference files.
(Mac OS) While pressing Shift+Option+Command+Control, start InDesign. Click Yes when asked if you want to delete preference files.
If that doesn't work, you'll have to find them on your computer and delete them. Instructions are here:
http://livedocs.adobe.com/en_US/InDe...cb3f-6d1e.html