I get an error message box when I start clamwin:

Error: Image file is not of type 3

Clicking OK clears the error message. When selecting a drive to scan and clicking scan same error message appears. Clicking OK clears the error box and the scan begins with no problem. NOTE: the above error message just appeared. ClamWin worked ok before.

Additional info: ClamWin portable ver:0.88.5 / Virus DB Version (Main:42, Daily: 2438). Installed on a Kingston Data Traveler 2.0 thumb drive. Running Windows ME on a Pentium II AMD-K6-2 500 / 384mb Ram.

we don't support directly clamwin portable since it works in a bit different way (for paths and other minor stuffs)
Your version anyway it's a bit outdated try to use 0.88.7