False Positives are common and I have yet to find a good way to convince owners about this. They remain convinced it is infected and may run off to another shop to get it removed. The results are similar to your story.
I wish there were not False Positives but if folk don't know, they lose a lot of time and money no matter what the antivirus company.
Friday morning, Avast alerted me that there was a suspicious "hidden object" (root kit) in my computer. After failing to get any results through my Avast software on deleting it, I called the number Avast had on the screen for FREE telephone support. BTW, I had just re-subscribed.
I talked to a representative, and told him that the Boot scan showed No Virus, but after Re-boot, Avast said the virus was still there. I ran the scan several times. He scared me with all this talk about losing all control of our computers (and having to replace them) unless I purchased the Avast Pro Support - $179, then, $299 when I said there were actually two computers on our network - 2 for $299.
After a Tech supposedly "fixed" my computer, and signed off, I rebooted, and got the same warning. I scanned it again. The report said "no virus". However, the alerts keep on coming. False Positive.
Meanwhile, another Tech - on the other computer - really screwed up, knocked off the wireless, and lost the connection, and signed off, so very little was even done. We were worried that the computer was really screwed up now. And, I don't think she even inserted the new license.
According to the internet, this False Positive Scan concerning the Win32:Evo-gen virus has been a known issue for months. It seems like most victims we've seen so far are customers of Avast. Avast is continuing to report a False Positive. The company should have known all of this by now, since it's been happening for so many months, and it's their job to keep up with all of this.
I put my computer through the same kinds of tests with other anti-virus companies, and they found No Viruses! Still, Avast says differently.
He gave me a new Avast Pro license, and my credit card company said there were charges around $500 from all this, pending. The first $179 was NOT even taken off, when I told him to go ahead, and fix the other computer also! I was charged twice!
All of this took up my entire day! They deleted all of my important cookies without even asking, and tossed my pricey PC cleaner in the Recycle Bin!
The Rep didn't tell me that there have been False Positives reported by Avast, and connected to the Win32:Evo-gen virus (or Trojan). Not only did he scam me, upset me, and waste my time,the total charges are over $500!!
I am shocked at Avast, engaging in these kinds of practices, and I will never trust this company again.