There could be an issue with the date settings in your articles, make sure your dates are correctly set:
- Start Publishing: Any past date
- Finish Publishing: Empty, or any future date
- Created Date: Any past date
I've sometimes copied existing articles and then edit the content, without changing the dates, wondering why my articles don't show up as expected.
Also, please make sure your articles are actually saved (maybe obvious, but simply in order to sort out possible errors).
Take a look at Lodders comment too, I've seen this happen before.