I am also in the same boat. I have good credit high-700s / low 800s and I checked my score a few days ago to find it at 590.
Iqor Canada is reporting an ETR debt from 1999 that I was first contacted about in 2005 and which had ballooned from something insignificant to just under a thousand dollars. I refused to pay it. Did now acknowledge it. They went away. In 2007 they sent me a bill again that I refused to pay.
Now 2009 and IQOR is reporting that the date of last activity was 06/09. I have written to IQOR and started an Equifax investigation. I have also written to the ETR and filed a complaint with Consumer Affairs. Is there anything else I should be doing?
I am considering civil action as the reason I was checking my score was because I was going to apply for credit that I needed for a large purchase. I have the resources to sue and I'm not really concerned if the legal fees are more than the award as I'd be just happy with making them pay. Is this an option?