ManTiger:
Though i'm not familiar with your question and i did not see anything of such on the cic page but don't worry cos fellows will come to your aid.

Amefrica:

You don't have to upload anything there, abi you didn't fill the questionnaire well nii. What did you choose here "have you done medicals in any of our designated clinics within the past 6 or 12 months (can't remember precisely as it is there tho)".?

Haustraliah:
You need to upload the following if online.
application for study permit outside Canada.
schedule one.
application for temporary residence visa.
common law and representative are filled based on conditions.
if you use and agent.
my ogas may add more.
good luck

Haustraliah:
It happened to me too,I later uploaded successfully.
To upload your certificate and some other documents like transcripts,etc,you combine them together through acrobat or word,so all your files will be view as a file,then upload.
NB..All uploading sections have limited megabites.
Good luck.