Virgin Media's broadband service is operational again following a national outage on Monday evening.
The disruption was caused during routine maintenance, a spokesperson for the cable operator told ZDNet.co.uk on Wednesday. According to the spokesperson, a scheduled firmware update "did not apply properly, causing the routers to reset". This in turn caused a mass of IP conflicts because of the "sheer volume of connections trying to reset themselves at the same time".
It is estimated that around three million connections were affected, although it is not known how many of those belonged to business customers.
Virgin Media was created by the merging of the two original cable operators — NTL and Telewest — and the mobile virtual network operator Virgin Mobile.
"At 9.20pm [on Monday] customers in a number of regions temporarily lost connectivity to their broadband and video-on-demand services. This occurred as a result of an error during a routine maintenance process which affected some customers' modems and set-top boxes," Virgin Media said in a statement on Tuesday. "Broadcast television and telephone services were unaffected."
According to the statement, most of the problems occurred in the North West, Yorkshire and the Midlands. Virgin Media claimed that most of the affected users were back online shortly after midnight, and the remainder were reconnected early on Tuesday. Virgin Media apologised to its customers "for any inconvenience this may have caused".