Amazon's cloud storage service has been experiencing high error rates since around 12:30 PM EST today.
Their service health dashboard has a notice near the top of the page indicating such.
Until their S3 web service returns to normal, the Related Links section will not be functional for uploading new files or downloading existing files from related links.
I will update this announcement again when things return to normal.
Update 4:10 PM EST: Files in Related Links can be downloaded again. Upload is still having issues.
Update 5:18 PM EST: Everything seems to be working properly again. Amazon announced S3 is working normally again.