The keyboard shortcut for viewing the baseline grid does not work in the CS5 Mac version. I can see the baseline grid by going through the menus but it would be so convenient just to press some keys as I am supposed to be able to. This must be a bug. I can view the document grid easily enought, either by going through menus or by using the keyboard shortcut (command + ').
When I type an apostrophe I do get an apostrophe. I have tried changing my language and keyboard settings to American - that really ought to work with InDesign but it still doesn't work. As I said, I can view the document grid easily enough. The only difference with the baseline grid is that you have to hold down the alt key as well. Why that should disrupt everything I don't know.
Yes I am using the default ones. I've checked by going to Edit - Keyboard Shortcuts... and looking at the menu. It says default throughout and it says that to show the baseline gird I should press Opt + Cmd + '. All other keyboard shortcuts work that I have tried but this one just doesn't!
I was getting the same problem (CS5). Fixed it by going to OS X System Preferences > Keyboard > Keyboard Shortcuts > Keyboard & Text Input > uncheck 'Move focus to the window drawer' which uses the same shortcut.