Since I don't own the Canvas theme, I can't tell you if changing between sidebar areas would help. I'm not sure what could be causing the issue on your site.
Here is what we know at this point:
- The problem doesn't seem to be caused by plugin conflicts, as you've tried to disable them and it didn't help.
- As I mentioned earlier, I can't reproduce on my end using one of the default themes.
That leaves us with one difference between your site and mine: the theme. I don't have access to the Canvas theme so I can't test things on my end, but since it's a premium theme you should be able to get some help from the Woothemes support team. They should be able to test and let you know if they can reproduce the problem on their end.