You may be able to pickup the correct threads using a BSC drive side cup (I would try this with a cartridge). Take the cup and carefull strat threading the cup while keeping it centered and straight. When it binds, tap it with a rubber mallet and try screwing it in some more; you may need to utilize a tool, but be vary careful. As long as the cup is going in centered and straight you'll be alright. If the cup slips off center, it is picking up the old crossed threads. Back it off until the cup it straight again, tap it with a mallet and try threading it again. The beginning of this process is critical you keep the cup centered and straight if it's going to work. If all you end up doing is chewing up the threads stop and take to your LBS. Also the reason why the non-drive lock ring unscrewed is usually because it was no torqued enough. The plastic lock rings are torqued as tight of as the alloy cups, but many are afraid to do so and it may cause the non-drive side to back out..