Sidebar and footer boxes overlap, causes issues with alpha backgrounds

OK so I have all elements on my site slightly transparent, and set them all at the same level of alpha (strength of transparency)

So they *should* all be indistinguishable.

BUT, it looks like you can see through the sidebar box through to the footer bar underneath.

e.g

Here's my site design:


sidebar and footer shown. I've temporarily coloured the footer blue to show the effect more clearly.

And here's a close up of the bottom left corner:


So, in my opinion the corner should be either the same shade of blue as the rest of the footer, or the same shade of white as the rest of the sidebar (accounting for the underlying background image).

This seems to be the only spot where site elements overlap. (and if the footer did start where the sidebar ended, it would mean the copyright text would be centered as though the side bar wasn't there, rather than now, which looks a little offset..

Hope that makes sense! Please let me know if not, and I'll try and clarify further.