Avast Cleared Computer Said HealthyChecked with Superantivirus!Trojan.Agent/Gen-

I have used Avast and depended on it for afew years. Bragged about it. Yesterday my computer was lagging and some pages would not load.
www.microsoft.com
www.cnet.com
www.amazon.com
www.ebay.com
and some others appeared to be in plain text without HTML.

I knew something hacked my computer. I ran avast and it bogged down and stopped. I tried Stopzilla, it said clean
then A You tube video on how to detect virus and trojans and malware gave a name of a malware I had not heard about. I was willing to try anything.
I downloaded Superantivirus pro and tried the trial version. It found
Trojan.Agent/Gen-Nullo[Micro]
WHAT???
I ran avast again and stopzilla again. I did not want to be dupped into buying something I did not need.
I also ran the new anti virus malware again.
cleaned out the trojan, rebooted and my machine was fast and all pages re appeared! WHAT???
Has avast not put this into their data packs???

SUPERAntiSpyware Scan Log
http://www.superantispyware.com

Generated 01/08/2014 at 02:57 AM

Application Version : 5.7.1016

Core Rules Database Version : 10935
Trace Rules Database Version: 8747

Scan type : Complete Scan
Total Scan Time : 14:47:43

Operating System Information
Windows 7 Home Premium 64-bit, Service Pack 1 (Build 6.01.7601)
UAC On - Limited User

Memory items scanned : 673
Memory threats detected : 0
Registry items scanned : 75429
Registry threats detected : 0
File items scanned : 186235
File threats detected : 1

Trojan.Agent/Gen-Nullo[Micro]
C:\USERS\ROY HAMLIN\APPDATA\ROAMING\APPLE COMPUTER\MOBILESYNC\BACKUP\9A6321B996BB089A1D8FC8094C98937B7BD5CC3C-20120613-041120\4EAFFC4BF2C3F2727F4B17E44A146B69C29C0A53

Has avast not put this into their data packs???
no security program have 100 % detection

run a scan quick with Malwarebytes. you can download it here. http://forum.avast.com/index.php?topic=53253.0

post log here