One thing you can try is entering one of the lines below into your hosts file.
www.auctiva.com 38.102.38.77
www.auctiva.com 38.102.38.78
www.auctiva.com 38.102.38.82
www.auctiva.com 38.102.38.83
www.auctiva.com 38.102.38.84
If the site then don't ever work either remove the line or change it to another.
This would be a temporary fix until we figure out why it's doing this randomly to some people.