Some Chicago-area RueLaLa.com shoppers are unable to access the web-only flash-sale site today, and the problem has persisted for more than 24 hours, says web site performance monitoring firm AlertBot.

RueLaLa.com, No. 84 in the Internet Retailer Top 500 Guide, sent out its daily marketing e-mail at around 10 a.m. Central time on Tuesday and Wednesday, alerting shoppers that the new limited-time sale was beginning. But on both days, some visitors in the Chicago area have seen a blank white screen, and the problem remained as of late afternoon today. 

Rue La La is aware of the site issues and is working to resolve them, according to a spokesman. The retailer would not disclose the source of the problem, but says it is affecting a small percentage of its customers.

The issue is a regional one, AlertBot says, because testing from other U.S. locations, including California, Colorado and Texas showed the site working properly.

“There are a number of issues that could cause this and it may be something very complex,” says Justin Noll, director of client services for AlertBot. “The HTML code is being delivered, so the web site is there, but it isn’t being displayed in the Chicago area.” Noll adds that the problem could be with Rue La La’s content delivery provider or other factors, such as human error in the adding of new files to their server.

Rue La La, which works with content delivery network Akamai Technologies Inc., did not respond to a request for comment. A spokeswoman at Akamai says their systems were running normally.

According to data provided for the 2012 Internet Retailer Top 500 Guide by web site monitoring firm Compuware Gomez, RueLaLa.com was available to site visitors 99.92% of the time in January 2012 and averaged a 1.29-second page load time. Compuware Gomez rated the consistency of the merchant’s web site loading time as excellent, meaning performance is roughly the same from one visit to the next.