Engineering work due to be completed over the Easter weekend has overrun leading to delays for commuters.
London's Liverpool Street station and all lines serving it were closed over the weekend for repairs at the station and in the Clacton and Shenfield areas.
Operator National Express East Anglia said work due to finish on Monday had overrun and delays of up to an hour on the line up to Norwich were expected.
The cause is signalling problems after track replacement at Shenfield.
Work at Liverpool Street station overran at New Year leading to an investigation by The Office of Rail Regulation (ORR).
'A complete standstill'
Network Rail was fined a record £14m after engineering work at Rugby in late December and January overran by four days causing massive disruption.
This was coupled with disruption in London when late-running work at Liverpool Street station forced it to close as people tried to return to work after the Christmas break.
One rail user in Suffolk, Alastair Chapman, earlier told the BBC: "Trains are at a complete standstill here at Stowmarket owing to overrun of engineering works by Network Rail at Shenfield.
"Clearly the lessons of 2 and 3 January have not been learned by Network Rail and nobody is being told when the works will be completed and the track opened."
National Rail Enquiries initially said delays were expected until midday, but disruption is expected until the end of the day.
National Rail Enquiries said services to and from Norwich to London Liverpool Street have been reduced to run hourly - departing on the half hour from Liverpool Street and on the hour from Norwich.
Brian Cooke, chairman of passenger watchdog body London TravelWatch, said late notice was given by Network Rail of the delays.
"It is utterly disgraceful that, after all the trouble over New Year, and after so many promises and assurances, that passengers have once again been severely delayed," he said.
"It is simply not good enough, and the industry should be totally ashamed of itself.
"Yet again, the information given out to passengers by Network Rail and National Express East Anglia was completely inadequate. The websites gave contradictory and wrong information and the phone lines did not work effectively.
"Passengers want, and deserve, better and we will be expecting plain answers from the industry."