This indicates an attempt to exploit a Denial of Service vulnerability in the SMB service of Microsoft Vista.
The vulnerability in the SMB service can be remotely exploited while protocol dialects are being negotiated. When the DoS condition is triggered, Vista no longer responds to SMB requests and existing SMB connections to the Vista host become unresponsive.
Microsoft Windows Vista.
Denial of Service: remote attackers can stop SMB from responding.
Upgrade to Microsoft Vista SP1.