I get the same error with Slackware 10.1, ens1371 module. This error has only just happened recently when I tried upgrading to the newest versions of ALSA on Slackware 10.0 and now happens out of the box with 10.1. Perhaps I'm way off base, but I think it's a bug in ALSA. All I know is that it worked flawlessly before and now no matter what I've tried, googled for, etc. nothing works
Nothing, that is, except using an old version of ALSA. I don't know if that's a viable option for you or not, but it's worth a shot.