I've posted a test release of Portable ClamWin AntiVirus:
http://prdownloads.sourceforge.net/portableapps/Portable_ClamWin_0.88.1_...
It's a 4.9MB download. 18MB installed before you download the definitions . Please give it a shot and post any comments or suggestions back here. This will be publicly released soon.
UPDATE 4/18 11:30pm EDT: The bug has been fixed. Please try it again.
UPDATE 4/19 10:45am EDT: Added fix for PCs without the latest MS VC files.