Thanks for suggestions...
I flashed the bios of the sound card and reinstalled new drivers. The problem went away, but when the computer came back up, the problem resurfaced. I went through this cycle several times: I could reinstall the drivers for the sound card and get AH to work, but when the computer rebooted, problem resurfaced. There was nothing obvious in Autoexec.bat or config.sys to cause the problem.
Rather than troubleshoot this problem for too long, we chose to replace the sound card with a Soundblaster live value, which fixed the problem. I may try the AWE64 in another computer.
Anyway, the problem is fixed and thanks for suggestions.