Red Baron, original release of Wolf3D, and a few others have it hard-coded also, but that's another story. Pole fixed his problem by using I5. What I am wondering, is if the game was designed around an older SB card, such as the original SB or the Pro models, which use I7, and putting an SB16 on I7 was screwing with the game? SB16 is native I5 and switching to it fixed the problem, so that makes me curious. Perhaps it works with I7 but expects an SB or SB Pro card, and throwing an SB16 at it was the issue?

I doubt it's your hardware, Pole. DOSBox doesn't take advantage of dual cores or hyper-threading, and it isn't a 64bit application, so it isn't going to use any of the special stuff your chip offers. I have a friend who had me build him a dual-core Pentium system a year ago and DOSBox runs fine on it. Next time I visit, I'll take the game on my flash-drive and test it there, but that may be a few days.

http://www.dosbox.com/comp_list.php?showID=1270&letter=B
One suggests that the irq can be changed in some setup file,
maybe (if it's configurable through the setup/installer) that setting
isn't saved or not written correctly.

Exactly, OR the setting is completely ignored and it looks for a specific card-type on a hard-coded IRQ. Red Baron does that, and I7 will prevent it from playing sounds, although the music plays fine, but I imagine that sues 330 for GM or something.

Doubt the setting is ignored.

I had the same problem.
I have two versions of the game, the one where the save files are called DEMOX.IM1 (game version is Ver f1.01 ) and that's where I can't get pass the access code, and the other version (which is Ver f1.02s) where the save files are called GAMEX.IM1 and I have no problem passing the access code part.

Both of these versions were downloaded image files and not from real legal CDs, I actually have the original CD but I'm too lazy to look for it among the 2000+ games in my storage...

Personally, I think that the first version is flawed, what you would call a "bad abandonware issue"...

[Edit]
Forgot the most important part... changing IRQ from 7 to 5 (in both DOSBox and setup) didn't solve the problem.