If your claim is that it is your ex-wife's debt and not yours, maybe you just need to send a copy of the divorce papers with your dispute to the credit agency to show it isn't your debt. You were already divorced when the debt was incurred, right?
Longer Answer: For others wanting to initiate the dispute process.
Source: US Federal Trade Commission Web Site.
How To Dispute Credit Report Errors
Under the FCRA, both the credit reporting company and the information
provider (that is, the person, company, or organization that provides
information about you to a credit reporting company) are responsible
for correcting inaccurate or incomplete information in your report. To
take advantage of all your rights under this law, contact the credit
reporting company and the information provider.
Tell the credit reporting company, in writing, what information you
think is inaccurate. Include copies (NOT originals) of documents that
support your position. In addition to providing your complete name and
address, your letter should clearly identify each item in your report
you dispute, state the facts and explain why you dispute the
information, and request that it be removed or corrected. You may want
to enclose a copy of your report with the items in question circled.
Your letter may look something like the one below. Send your letter by
certified mail, “return receipt requested,” so you can document what
the credit reporting company received. Keep copies of your dispute
letter and enclosures.
Credit reporting companies must investigate the items in question —
usually within 30 days — unless they consider your dispute frivolous.
They also must forward all the relevant data you provide about the
inaccuracy to the organization that provided the information. After
the information provider receives notice of a dispute from the credit
reporting company, it must investigate, review the relevant
information, and report the results back to the credit reporting
company. If the information provider finds the disputed information is
inaccurate, it must notify all three nationwide credit reporting
companies so they can correct the information in your file.
When the investigation is complete, the credit reporting company must
give you the results in writing and a free copy of your report if the
dispute results in a change. This free report does not count as your
annual free report. If an item is changed or deleted, the credit
reporting company cannot put the disputed information back in your
file unless the information provider verifies that it is accurate and
complete. The credit reporting company also must send you written
notice that includes the name, address, and phone number of the
If you ask, the credit reporting company must send notices of any
corrections to anyone who received your report in the past six months.
You can have a corrected copy of your report sent to anyone who
received a copy during the past two years for employment purposes.
If an investigation doesn’t resolve your dispute with the credit
reporting company, you can ask that a statement of the dispute be
included in your file and in future reports. You also can ask the
credit reporting company to provide your statement to anyone who
received a copy of your report in the recent past. You can expect to
pay a fee for this service.
Tell the creditor or other information provider, in writing, that you
dispute an item. Be sure to include copies (NOT originals) of
documents that support your position. Many providers specify an
address for disputes. If the provider reports the item to a credit
reporting company, it must include a notice of your dispute. And if
you are correct — that is, if the information is found to be
inaccurate — the information provider may not report it again.
Be sure to check out the site linked above. It even includes a template dispute letter that you can use.