Your browser basically gets cluttered with "twin sets" of tabs? Does this happen randomly or is it the result of an action? Certainly looks like a mess!
EDIT: On a side note, I've used Opera a bit, and it seems to be the only browser with the option of "Duplicate This Tab", or something along those lines. In other words, I could right-click a tab, select that option, and then a tab with the same URL pops up next to it. As far as I know this is not possible in Firefox or IE.