The problems concerning Glasgow Doors Open Days have caused the Glasgow Building Preservation Trust to abandon the bookings on its website.
Ticketing will now be through a relaunched web page today, hosted by a separate company, eventbrite.co.uk.
Now in its 24th year, the heritage festival offers free access to 100 buildings, with dozens of tours and talks from September 16 to 22.
This year's programme has been themed around railways, the 2014 Commonwealth Games and the Green City and organisers said the problems had been brought about by massive demand.
The troubles began when some 5000 people tried to log in to the bookings site at 9am on Tuesday, causing it to crash. It then failed to open twice on Wednesday and crashed again. Since then nobody has been able to book tickets as the site continues to fail.
Unknown to the Trust and their technicians, 200 people had been able to book tickets, and organisers said they would be honoured, despite complaints from some users that would be unfair.
Highlights of the festival include open trips down the vaults of Central Station, with visitors also given access to the famous glass roof.
One user said: "Trying to book this year's events has been a shambles. Apparently the reason is popularity for Central Station, which led to unprecedented demand and the system crashing.
"However, I now learn that nearly all the places for this venue are full and there is reason to believe they were filled by people who went on the booking system before the official opening times."
Despite frantic attempts to get the site active, the Trust decided yesterday to abandon it and was looking at the alternative solution.
Anne McChlery, of Glasgow Building Preservation Trust, said: "We are extremely sorry this has happened and realise this is very disappointing for visitors. We have been working hard to remedy this.
"Although this is not ideal, it has highlighted the popularity of the event and we are astonished at the amount of traffic the website has gained, not to mention the number of phone calls we have received.
"We would like to reassure everyone we will be taking this year's lessons into consideration in future years and will be readdressing our booking registration system to ensure this does not happen again."
This year's event is also to include 2014 Games venues, including the Athletes' Village, Glasgow Green Hockey Centre, Hampden, Kelvingrove Park tennis and bowls pavilion and Tollcross pool.