Firefox mouse buttons question

[gsiliceo]

Hi i've mapped my mouse buttons 4 and 5(thumb buttons) with btxn to middle click so in any application when i hit those buttons i get a middle click button wich is fine, the only place when it doesn't work is in firefox, firefox does both things at the same time when i click the 4th button it sends a middle click AND a 4th button click(wich it makes the current page go back) so i get a back button and a middle click at the same time.
Any idea on how to stop firefox from treating the 4th button like a 4th button and start behaving like the rest of the apps that do listen to my bindings?
thank you very much

firefox: 3.6.3
lucid lynx: totally upgraded
btnx from repositories

[gsiliceo]

it turns out it was btnx fault, because it sends the signal of the "middle click" AND the "back one page" the official manual says its a known problem and they can't do anything about it, it suggest that i make sure that i'm not using the evdev driver, anyidea how to stop that driver?