This is a strange problem in DNN 3.0.12 when I log in as host and am able to see and modify page settings, but none of the modules are showing the editing icons, so I can't edit any content.... When I login as Admin the same thing happens. I cannot recall doing anything wrong, last time I edited a few pages, then logged out, no problem. I looged in half a day later, and it seems like there is some kind of lock-out on content...
anyone has seen this problem before?

Yep, sounds to me you have the 'Preview mode' on. Check if you have it 'checked' on top of the page. If there is a 'plus' sign in the magnifying glass, you're in preview mode. Click it to change to 'normal' mode.

Oh, how tricky..! The preview must have been turned on  -but there is no easy way to see it, just the change in the icon, so unless you'd notice the different icon it is not obvious. Anyway, it WAS preview mode, thank you!

Don't feel bad... many a core team member (including myself) has occasionally gotten bit by that.  Wer'e thinking of making the icon a big red flashing button *grin*.