At midnight on New Years Eve, key software at the Denver Marriott Tech Center failed, locking guests out of their rooms and causing chaos on hotel grounds.According to a letter given to guests by hotel management, the buildings room key software crashed at midnight on Dec. 31.A hotel guest told 7NEWS that people were locked out of their rooms for hours and that riots broke out in the hallways.Denver police spokesman Detective John White said an officer requested assistance in the parking lot of the hotel at 4900 South Syracuse Street at about 12:40 a.m. Sunday due to a large disturbance. There were reports of several assaults connected with guests who were unhappy about not being able to get into their rooms.White said police were also investigating reports of assaults and property damage inside the hotel. No one was arrested.A letter from hotel management admitted that the issue caused significant inconveniences and said that all guests would be refunded for their room charge and taxes for Saturday night.Hotel guest Rachelle Mathis said the scene was chaotic. She described people urinating in hallways.It was not the celebration Mathis had planned. She said she spent part of New Years Day giving a statement to Denver Police.It was terrifying, Mathis said.