It looks like they resolved the issue:
From: SenderBase Support [mailto:firstname.lastname@example.org]
Sent: Friday, October 29, 2010 2:18 AM
To: Alex Melen
Subject: RE: Re: [IronPort.com #637129] Fwd: Poor Email Reputation
Caution: When replying, please do not remove the reference id (ref:) at end of email thread as it is the tracking tool for this ticket. Removal will create a separate ticket for your response and will result in delays to the resolution of your inquiry.
Regarding your inquiry:
The discrepancy with the IP range has been addressed and the IPs have all improved.