Redshoe - if you have not ditched this kit, you can try to salvage it. Just hold the bag over your primary bucket and puncture it with a clean knife - the juice will flow out without any "explosion". If the juice smells and tastes ok, you can continue to make the wine. If not, throw it out as suggested.
I have had a couple of kits do this and they turned out fine. Somehow, fermentation has likely begun in the bag - perhaps a latent yeast that has just waited for the right conditions. In my case I added the kit yeast and it, as far as I know, overpowered the original yeast and completed the process.
You have nothing to lose by trying this - good luck.