It seems like currently stumbleupon social button does not support SSL/https:// environment yet.

Reference link : https://getsatisfaction.com/stumbleupon_help_center/topics/ssl-issue?topic-reply-list%5Bsettings%5D%5Bfilter_by%5D=all&topic-reply-list%5Bsettings%5D%5Breply_id%5D=16271275#reply_16271275

I am suffering from the same problem. I simply went into social integration and disabled stumbleupon button. Then I went to the stumbleupon forum in the link above and made a new complaint. Perhaps if you and others do the same they will finally look into the issue.

Thanks for sharing.

I received this reply from StumbleUpon:

CH (Official Rep) replied to this problem:
Share buttons won't work in SSL environment
We have no immediate plans to support this issue with relation to Https:// - sorry about that.

Looks as if those of us that run in a https environment will just have to disable StumbleUpon sharing. Really sad as I liked being able to share via SU.

Sorry, there is really nothing we can do as these are being generated by Stumble Upon