I do not have any hardware similar to your setup so I doubt that I can be of much help (feel free to ignore the following suggestions).
Could you provide the chipset model for your motherboard soundcard? (Some chipsets which provide combined audio/ethernet functionality make it difficult to disable sound without also disabling the ethernet).
Also, have you investigated the envy24control
utility? (I believe it is for you M-Audio card).
Have you seen the comments at the bottom of this page
pointing out some possible BIOS settings?
Finally, you may wish to see if you can record audio using MHwaveEdit
. One of my 'puters records hideously using Audacity -- though the symptoms are different from your description -- yet MHwaveEdit records fine (I have yet to track down the Audacity problem).
This is not the motherboard sound card but an aftermarket one, the M-Audio Delta 410. It apparently uses the ICE 1712 chipset. The on-board sound card has been disabled in the BIOS.
Like the last respondent before this post, I found Audacity worked just fine with other distros. Vector Linux obviously has some major multimedia bugs in it.
I don't know if I really need to install new software or drivers. The card works fine with XMMS, MPlayer and VLC. Only AUDACITY is giving me problems. This seems to be a kernel-level issue, as I downloaded the source code for Audacity and compiled it, and re-installed it on my system, bypassing the VL repositories (my thought was that their install files for Audacity were corrupted).
As for those comments, they were obviously written by someone with a lot more hardware experience than I've got. I'd prefer not to experiment, especially since this problem seems to be peculiar to this one application.
As for MHWavedit, I'll check it out.