Hi, I am also having the same problem. Here is what support had to say:
Hello,
I apologize for this inconvenience however, I appreciate you bringing this to our attention. Our engineering department is currently investigating this issue and will have it resolved as soon as possible most likely in the next few hours. In the meantime, this may be an intermittent problem. In which case trying your upload again could remedy this issue.
Please let me know if you have any further questions.
Thank you,
Auctiva Support