You wouldn't believe how huge it is. It is possible that your account was VAC banned based on violation reported as placed from your IP. It might've been not you, but your neighbor - you simply got his IP in lease due to dynamic IP's rotation. The chance that you get the same dynamic IP again or IP address of another hacker/cheater/scammer in your area is pretty high considering retarded mechanisms ISPs are using to rotate their DHCP leases.
So until you get to the bottom of this case with Valve, DO NOT spend any money on your "fresh" account which Valve may consider to be an alt, by the way.
Valve VAC FAQ said:If you choose to purchase a new copy of the game, please register it or install it under a newly-created Steam account.
I also read in the faq that the VAC does not track IPs, just accounts/SteamIDs