For example:

*I edited URL because it's now irrelevant *

The side block to the left is floated however it seems padding and clear:left within the main #content div is still catching the external left side block div.

Any suggestions?

I don't see anything wrong in FF3 or IE6 ..

My apologies, I floated left and set width. Would have liked it for #content to have been 100% width and a bit more flexible without those bugs.