UPDATED 04/26/12 1:52 p.m.

HIGHLAND PARK, Ill. (CBS) — Customers flooded the Ravinia Web site to buy concert tickets on the first day of sales Thursday, and many are complaining that they had to wait online for hours.

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Tickets for the 2012 season at Ravinia went on sale at 5 a.m. Thursday. Customers logged into the Ravinia Web site right away in hopes of being first in line.

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But in Facebook comments posted Thursday, many customers complained that they had to wait in a virtual line for tickets for several hours.

“What an absolute train wreck of an experience,” one man wrote. “I was able to confirm purchase of Santana tickets but the site crapped out as I was buying other tickets. By far the worst experience ever buying tickets for Ravinia events.”

Ravinia posted a notice on its own Facebook page to reassure customers.

“Ravinia’s systems are not down. This is the first day of sales for more than 100 events, and demand is high. That means wait times are much longer than usual–30 minutes or more. Please be patient. As long as you see the orange communications bar from Ravinia on your screen, you are still in line,” Ravinia said on the page.

But some customers said they were stuck waiting far longer than 30 minutes.

“I’ve been waiting nearly 4 hours online to buy tickets. This is the worst experience buying tickets,” a woman wrote. “Thirty minute wait time? That’s a load of crap.

“I don’t understand this. I’ve never had a problem getting tickets at 5 a.m. before. I’ve now been holding my ‘place in line’ for over 3 hours,” another woman wrote. “I was even going to splurge on reserved seats this time, but it sounds like the shows I wanted have already been sold out.”

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Many others reported logging into the Web site using multiple computers, smart phones or tablets before getting through.

In addition to the Facebook notice, Ravinia also sent out an e-mail earlier this week, warning customers that the venue’s Web site would be busiest between 5 a.m. and 1 p.m. Thursday.

“You will likely be held in queue for some period of time if you are trying to buy tickets during this time. If you see the orange message on screen, you are in queue. Just be patient. Opening additional browser windows won’t help,” Ravinia said in the e-mail earlier in the week.

Ravinia Festival spokesman Nick Pulia said the volume of traffic for first-day ticket sales was up by a factor of 3.75.

“That is about three times longer than last year; at the peak, it was around 10 minutes, so it’s like three times longer,” said Ravinia Festival spokesman Nick Pulia.

Pulia said 9,000 people at a time were jamming the Ravinia Web site Thursday morning. Last year, it was only 2,400.

“Three shows are completely sold out – pavilion and lawn – and six shows, pavilion actually is out,” he said.

The concerts by James Taylor, Train and Santana were all completely sold out as of early Thursday afternoon.

The headliners at Ravinia this year include Colbie Caillat; Earth, Wind and Fire; Macy Gray; Glen Campbell; Hall and Oates; and Duran Duran.

Ravinia favorites such as James Taylor, Tony Bennett, and Garrison Keillor’s live performance of “A Prairie Home Companion” will also appear.

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Ravinia advises anyone having trouble processing an order e-mail the venue at tickets@ravinia.org.