extension.mismatch

A few days ago I did a scan with Malwarebyes and I found a file was infected with Extension.mismatch. I posted on their forum asking what it was and nobody could tell me, so I just wondering if anyone here can help me. The file was quarantined and deleted. Also the weird part was Norton or my other anti-spyware/malware progrom never picked it up. And I did a scan with Malwarebytes the night before the file showed up as infected was totally clean with no issues. Any incites would be appreciated. Here is the Malware log.

 

Malwarebytes' Anti-Malware 1.51.1.1800
www.malwarebytes.org

Database version: 7529

Windows 6.1.7601 Service Pack 1
Internet Explorer 9.0.8112.16421

8/21/2011 7:15:20 PM
mbam-log-2011-08-21 (19-15-20).txt

Scan type: Full scan (C:\|D:\|)
Objects scanned: 341006
Time elapsed: 41 minute(s), 45 second(s)

Memory Processes Infected: 0
Memory Modules Infected: 0
Registry Keys Infected: 0
Registry Values Infected: 0
Registry Data Items Infected: 0
Folders Infected: 0
Files Infected: 1

Memory Processes Infected:
(No malicious items detected)

Memory Modules Infected:
(No malicious items detected)

Registry Keys Infected:
(No malicious items detected)

Registry Values Infected:
(No malicious items detected)

Registry Data Items Infected:
(No malicious items detected)

Folders Infected:
(No malicious items detected)

Files Infected:
c:\Windows\serviceprofiles\localservice\AppData\Roaming\peernetworking\f233ed93c8f373da83543a30503cbcb33b7981c3.homegroupclassifier\adf46a35e32974f8ce07a32b2aa4a533\grouping\edb0025D.log (Extension.Mismatch) -> Quarantined and deleted successfully.