Chlorine Dioxide Troubles

I recently tried for the first time to use chlorine dioxide tablets while washing yeast, but after washing and then feeding with sterile wort for storage, my yeast is still not showing any signs of life after 36 hours. I used the potable aqua tablets that Northern Brewer sells and for the most part followed their procedure, except that I used two tablets because I had a 2 liter sample. Also, I meant to let it sit for four hours, as that seems to be the recommended time, but didn't end up getting back to it for six or seven hours. I then decanted off the liquid and topped it off with 1.5 liters of sterile wort.

I'm trying to figure out what went wrong, if I killed my yeast, or if they were maybe just not very viable to begin with (I used a yeast cake that had been sitting for about two weeks). Searching on the forums, I read that someone used foil to cover the yeast while the chlorine dioxide was reacting, to allow the gas to escape; I had the bottle sealed with a cap, so now I'm wondering if this may have had an effect or caused the chlorine dioxide to be contained so that the effective concentration was much higher. If anyone could share some insight, that would be great.

So to test whether or not the yeast was dead, I left it out overnight and I'm still not seeing any activity. I may have to break out the microscope and do some staining to check viability. I did leave some of the ClO2 liquid in the vessel when I added the fresh wort (diluted by maybe a factor of 4 with the wort), so now I'm wondering if maybe remaining ClO2 is inhibiting growth; is this possible? Any thoughts?