Hey, thanks guys. I'm using Sigl v. 0.9.3, and epub3-itizer v. 0.3.5 -- and yes, I got all those errors right after simply running the filter on my valid EPUB2 file and then running that through epubcheck. A lot of the errors (as opposed to warnings) had to do with width tags in images and tables, and valign tags in tables, which I switched out to the CSS equivalents -- I'm still stuck with all those warnings, though (289 of them), which I still don't understand the meaning of, and then I got more errors once again when I added in the audio file/code (as I mentioned earlier).
So I guess there is a bug, if it's supposed to come out "perfect." Either that or there's something wrong with my book that's crashing the script when it runs -- but it validates just fine (in EPUB2) so I have no idea what/where there that might be.
So yeah, I guess any help in getting things right would be much appreciated!