Unable to commit changes to repository

So I am a bit baffled as to what is happening when I attempting to commit a change to my plugin’s repository. As an FYI, I use Cornerstone App to manage all of my repositories.

I am able to log on and check out a working copy with my www.ads-software.com credentials. When I attempt to commit any change, I am met with the following error:

Commit failed (details follow):
MKACTIVITY of '***************': authorization failed: Could not authenticate to server: rejected Basic challenge (https://plugins.svn.www.ads-software.com)

Am I doing something wrong or has anyone else experienced something like this before?