It was probably an infected file removed by your Anti-Virus or some other AV or AM scan.
The best thing to do probably is follow the directions below.
We don't work on Malware removal in the general forums.
Please print out, read and follow the
directions here, skipping any steps you are unable to complete. Then post a
NEW topic here.
One of the expert helpers there will give you one-on-one assistance when one becomes available.
After posting your new post make sure under options that you select
Track this topic and choose one of the Email options so that you're alerted when someon has replied to your post.
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