Virgin Media suffered an outage this week after a router failed, preventing customers from accessing webmail, online bills and TV schedules on the site.
The router failed at 10.30am on Monday and was one of the principal devices used to control network connections to the site.
As a result of the problems, many visitors were unable to view the site, but others succeeded in accessing it when their traffic was directed through another working Cisco router. Customers who could not access the main website were also unable to access Virgin Media and NTL World webmail.
Additionally, when their traffic was redirected to other routers, those systems struggled with the traffic and caused the site to function slowly.
A spokesperson at Virgin Media said that the problems were resolved around 2pm when a card in the router was replaced.
"At approximately 10.30am this morning, customers trying to access Virgin Media's website or their NTLworld email through the webmail system may have experienced an intermittent service. This was the result of a hardware failure on one of the routers that deliver pages from these sites to customers," the ISP said.
Virgin Media apologised for the problem.
See also: ITV Player comes to Virgin TV customers