I second that. Did you check the art submission policy?

Fan Art

Dimensions and Size:

* Filesize: 1 MB maximum
* Width: Maximum 1500 pixels, minimum 400 pixels
* Height: Maximum 2000 pixels, minimum 350 pixels

Fan Characters:

If you draw an original character who exists in an existing franchise then file it under the category of that franchise and click the "fan character" checkbox. For example if you draw yourself as a character of Naruto, then submit it to the Naruto category with the 'fan character' checkbox checked.
Fan Comics

Dimensions and Size:

* Filesize: 1 MB maximum
* Width: Maximum 1500 pixels, minimum 400 pixels
* Height: Maximum 2000 pixels, minimum 350 pixels

Cards

Dimensions and Size:

* Filesize: 300 KB maximum
* Width: Exactly 350 pixels
* Height: Exactly 350 pixels

Or just check this site

Hope that helped

ive never ahd that happen before.....
i guess u shud make sure its in jpg format
and the size is correct
and if its stil lnto working
well, i guess log out then back in and try again.
im nto really sure.