If you did something wrong, your butt could be grass. They may want to talk to you about the investigation because your computer may be part of it (someone may have used your info for the scam).
I remember reading a report where the FBI confiscated some guys Linux machine because it was being used (unknowingly) for an overseas scam. The guys used Linux to share their cable modem, but never even thought about security aspects of the box. Someone hacked it and was using it for a long time.
Just be honest, don't get scared and cooperate. If you didn't do it, you'll be fine. If they start pressing you, find a lawyer.
vash