Be sure to just give the sync button a quick tap when you are changing modes, if you hold it down it might cause the 360 controller to re-sync with the xbox (all 4 lights going nuts). And of course the old suggestion (I know everyone gets tired of hearing this one) - be sure to try a fresh set of batteries
Please come back and post your results let us konw if you are still having troubles.
Also I think the fast reload isn't on/off, doesn't it like scroll through all the guns before turning off (on the CODMW2 works driver)? So you might have to go all the way through. You might want to check out the custom preset editor in the software forums, so you can build your own custom drivers and exclude any guns you don't use.