HI Bill, (1) are you using the debug library? if so, then try without. (2) an asset error means you've hit a condition that the Tableau developers didn't expect. If you can come up with a reproducible test case, contact Support and let them know. (You can also report this without a repro, but if you can't repro it, then Tableau may not be able to find the problem.)
I was using tableau-2.js. I switched to tableau-2.min.js, and so far, after about 4 hours, it is still running without the error. Thanks so much!