Talk with a local consumer lawyer, but don't expect to receive a large jackpot as a result of this minor mistake. Hope this perspective helps!
You are mistaken. A credit bureau does not have to respond to your request in 30 days. Rather, when the credit bureaus receive a dispute about a debt, they notify the furnisher of the dispute (i.e. the creditor). If the creditor verifies that the information is correct, it stays; if the creditor does not verify the information in 30 days, the credit bureau is supposed to remove it.
Credit bureaus make their money from creditors, not consumers. The credit bureaus listen to the creditors, not the consumers and credit reports are filled with errors. You can only sue the credit bureaus (and not all states recognize private causes of action against the credit bureaus) if there is erroneous or inaccurate information that the credit bureaus have failed to correct. If you are alleging that an error occurred in the reporting of information, you can recover up to $1000 per violation or your actual damages (if you were denied a loan or forced to get a loan at a higher rate because of the failure to correct the error). You also can recover reasonable attorney's fees.
If you think that a bona fide error/inaccuracy occurred, then you should talk to a consumer law attorney who specializes in FDCPA/FCRA violations.