Students at the Hawthorn Centre in Penge, south London, are among those who have suffered frustrating delays.
They say the problem, which has existed since May, is worst between 11am and 2pm, when the response is so slow that they cannot use the computers.
The centre is among 250 institutions around England to sign up for UfI courses, many of which have faced severe disruption. Delays have affected other centres to varying degrees.
It is feared the system may be unable to cope with the thousands of learners expected to sign up when Learndirect launches fully in September.
Brian Sutton, the university's IT director, said he was aware of some "access difficulties" but insisted that the network would be able to support the large numbers of students expected to take Learndrect courses in the years to come. He added that learning centres weren't being charged for the service during the development stage.
"I do have confidence that we have a system that can respond to the level that is necessary," he added. He said that much progress had been made in the 12 months since work commenced on the project.
"The system is serving up learning opportunities and we have registered between 4,500 and 5,000 since we launched the Learndirect website on May 15," he said.
Fine-tuning of the UfI's computers would continue in coming weeks to help increase download speeds, Mr Sutton said.
A new page should take no longer than two seconds to appear on a user's computer.
At this stage the Learndirect website is only available to usersfrom 9am to 9pm weekdays and 9am to 12pm on weekends so that changes can be made by technicians when necessary.
or the University for Industry at www.ufiltd.co.uk