Hundreds of passengers travelling north were forced to disembark at Carlisle and were ferried to Glasgow and Edinburgh by taxi or minibus after Network Rail closed the line.
Passengers travelling south were also ferried from Scotland to Carlisle, before travelling on by train. ScotRail had to cancel its sleeper service.
Network Rail said it had been alerted to the problem at around 2pm.
Engineers were dispatched to inspect the site, near Gretna, and discovered "significant damage to overhead line equipment over a considerable distance". It is unclear what had caused the damage, but Network Rail also described the Carlisle-Glasgow line as being blocked in both directions, suggesting equipment may have also fallen on to the track.
Virgin Trains was optimistic the issue would be resolved in time for the morning rush-hour.