I have had that before, the error that is, some of the virus' are very intelligent and they add a bit of code to the anti virus software to avoid it removing the virus. You really need to be sure its gone, have you tried looking up the virus to see what it does? a simple google search will usually tell you then you can see what you need to do from there. WHATEVER YOU DO DON'T SEND ANY PERSONAL DETAILS I.E BANKING ETC UNTIL YOU ARE SURE ITS NOT THERE OTHERWISE YOU COULD END UP HAVING YOUR ACCOUNTS EMPTIED!!!!.
This cannot happen from a virus, but it can happen, and has happened, from the rbot trojan. this particular trojan allows remote access to ones computer, the rbot trojan will monitor and steal passwords at free will.