Just to add my .02 here. I am also in the process of disputing inaccurate information on my and my husband's credit reports. I have had some luck getting inaccurate information removed, but have also had some that came back saying "verified" and were still not accurate.
If you are disputing something and it comes back saying "verified" or if it has been updated and is STILL inaccurate, you can continue disputing it as inaccurate. The credit reporting agencies HAVE to fix it. If they are telling you they have already investigated something and won't do it again, they are violating the law.
When re-disputing, I have found it helpful to point out what is wrong specifically. My first attempt is always a general attempt at disputing. I simply state "this account is wrong" and provide no more information than that. More often than not, the item has been either removed or fixed. But if I get it back and it's still wrong, I write back and point out specifically what needs to be fixed and if you have proof, that's even better!
Good luck! It is quite a chore--but hopefully it will be worth it in the end (at least that's what I'm hoping)!