Just happened upon this thread, although it doesn't appear to have the solution.
I just checked my hotkey settings, and there aren't any red entries or duplicated key combos. I've reassigned prev/next tab to "Num 1" and "Num 2" to mimic Opera. "Ctrl + Up Arrow" works fine for "Go UP", so the problem isn't the Ctrl key.
edit: I just reassigned back/forward to different hotkeys, tried pushing Ctrl+Back/Forward, and nothing happened... I guess this means there was no conflict.
edit again: If I try to use the Ctrl+Back/Forward hotkeys in the right pane of a dual mode lister, nothing happens. It only works with the left pane focused, and always opens in the right one.