Have you made sure the dropdown for the country is NOT BLANK ?
Also, if you keep trying to post something and get errors, the ad may still end up being posted, please be courteous and see if you have posted multiple instances of the same ad, and if so, please delete them.
Yes all required fields are filled out. If I go to "modify ads" they all are there (dozens of them) so I was able to post one of them by modifying it. It will not let me include a picture or fill in the make, model, serial # etc. Very strange and annoying.