Okay. Version 1.5 it is! ;)

When you were asked about the cs.sound.dll, did you allow it (clicked YES) or not (clicked NO)?
Same for the Captain_Sim.b767.sound.GAU?
I know that sometimes you can accidentally click on NO when you mean YES, which is why it's a stupid idea from MS, but nevertheless, it's there and we sometimes make mistakes because of it.

You could try opening the fsx.cfg, by entering this %APPDATA%\Microsoft\FSX\fsx.cfg in the search programs and files that shows up on clicking START (Vista/Win7), OR by entering it in the RUN command (WinXP), and removing all the CAPTAIN SIM 767 entries listed in the [Trusted] section. They will look similar to these:

J:\Flight Simulator X\Captain_Sim\767\cs.sound.dll.nqienoeouinoabhqqwhanqekwlwatteninbzwazc=1
J:\Flight Simulator X\Captain_Sim\Captain_Sim.b767.menu.dll.teowracutronhhkbaaretieoaleuoqbhwrzwkibb=1
J:\Flight Simulator X\GAUGES\Captain_Sim.b767.sound.GAU.acalhkquwrezrtnkehrccaokarnnanbqrciakcck=2
J:\Flight Simulator X\SimObjects\Airplanes\CS_B767-300\panel\Captain_Sim.b767.300.GAU.whzhrlqkeulthunoqtlrqizornzluwhczbweborz=2
J:\Flight Simulator X\SimObjects\Airplanes\CS_B767-300\panel\Captain_Sim.b767.adi.GAU.ouwhurernlrkrnathbhitbirrlqnbwqubcbbihbu=2
J:\Flight Simulator X\SimObjects\Airplanes\CS_B767-300\panel\Captain_Sim.b767.eicas1.GAU.ltqzbakzeoarorwuunctlaebzubbbikozrbzczke=2
J:\Flight Simulator X\SimObjects\Airplanes\CS_B767-300\panel\Captain_Sim.b767.eicas2.GAU.nwneutarkwielrkoouezlwthwzbrlbccknukcrkw=2
J:\Flight Simulator X\SimObjects\Airplanes\CS_B767-300\panel\Captain_Sim.b767.fms.GAU.howwawrtlkucuhckkueheclrkbaaluwzkeezclaz=2

I suspect that either the first or third entry, OR both the first and third entries, may be missing, which might be why you don't hear the sounds.

Hope this helps.

Mark