I'm having a lot of trouble with posting a photo to the photo contest as well. I am using windows 8.1, explore 11 and have tried posting a photo using:
Quick reply, I'm able to select the file on my computer but nothing happens after that.
Go advanced, I can select the file and hit upload and after a while I get an error message.
A link from my skydrive, can't do this because I don't have enough posts.
Not sure what the issue is. After a couple days of trying I was able to post a picture for the Autumn photo contest, but with similar trouble. Any help would be appreciated.