I had a detection while running the virus database update that occurred near the end of the process. After uploading to and scanning with both http://www.virustotal.com/ and http://virusscan.jotti.org/en I believe it to be a false positive. The following are the links to the results
http://www.virustotal.com/file-scan/report.html?id=f0e2447e6325ddf4428fd...
http://virusscan.jotti.org/en/scanresult/96d4f503699bde552a0787b70d6c3fd...
I had a similar result yesterday and attempted to report it as a false positive, although I am not sure if it took or not. I was able to complete the update by disabling avast temporarily, which is a possible workaround to this until it is fixed. I am including the log update relevant portion of the update log file below for those who may be interested.
ClamAV update process started at Fri Jan 06 14:20:03 2012
main.cld is up to date (version: 54, sigs: 1044387, f-level: 60, builder: sven)
Downloading daily-14256.cdiff [100%]
Downloading daily-14257.cdiff [100%]
Downloading daily-14258.cdiff [100%]
Downloading daily-14259.cdiff [100%]
Downloading daily-14260.cdiff [100%]
Downloading daily-14261.cdiff [100%]
Downloading daily-14262.cdiff [100%]
Downloading daily-14263.cdiff [100%]
Downloading daily-14264.cdiff [100%]
Downloading daily-14265.cdiff [100%]
Downloading daily-14266.cdiff [100%]
WARNING: [LibClamAV] cl_cvdhead: Can't open file E:\PortableApps\ClamWinPortable\Data\db\clamav-89c040633f12855ba54eff9f607b0436.00000780.clamtmp\clamav-ff2589ecdd0a1c0dd48d8190085ce2bb.00000780.clamtmp
ERROR: Can't parse new database E:\PortableApps\ClamWinPortable\Data\db\clamav-89c040633f12855ba54eff9f607b0436.00000780.clamtmp\clamav-ff2589ecdd0a1c0dd48d8190085ce2bb.00000780.clamtmp
Multiple antivirus apps running and updating will sometimes step on each other. It'll happen.
Sometimes, the impossible can become possible, if you're awesome!
Yesterday was the first time I ever had it happen to me. Just figured I would post the info in case someone else runs into this