VMware Inc. is having trouble getting VMware Fusion 3.0 out its download door and is getting customer complaints about timeouts and licensing problems.

Shortly after the software was released Tuesday for download by customers, VMware issued a support alert about its upgrade portal, blaming "overwhelming demand" for the upgrade problems. The alert remained on the Web site early this morning.

Fusion 3.0 is virtualization software that allows Windows, and other guest operating systems, to run on Intel-based Mac OS X. VMware Workstation 7 , also released Tuesday, is a virtual machine platform that supports multiple operating systems on a PC. Most of the VMware portal problems appear to be with Fusion.

One problem was difficulty in getting activation codes for the new products. In a blog post , Pat Lee, director of VMware's personal desktop products, posted the 30-day free trial key as a workaround.

"Because we've seen even more demand than anticipated, the VMware Fusion upgrade portal is having significant problems keeping up with the demand," wrote Lee, in a post Tuesday afternoon. "While we have already transacted thousands of upgrades today and many people are able to get the product, I apologize immensely to those of you who are anxious to get the product immediately and are running into issues."

Responded one user, Miku, in a comment field: "I'm very happy that you posted a temporary serial for us to try it out, the license server problems were driving me insane, I was really thinking I was insane."

Rob Enderle, an independent IT analyst in San Jose, said the demand for the product would imply that a lot of people suddenly want to run Windows on a Mac, "so many that it is crashing VMware's servers."

"VMware is largely a server company and not really used to the kinds of numbers that can be generated by a popular desktop offering. You jump from 100s for a server application to millions for a popular desktop application under load and this looks like VMware wasn't ready for this jump," Enderle said.

The site issues may be an indication that Paul Maritz, VMware's CEO, who was appointed last year and is a longtime Microsoft veteran, may have assumed that the demand was anticipated by his staff, Enderle said. "This should be one hell of a wake-up call for him, not unusual for a new CEO, and it will remind him that he needs to test his assumptions, because what he assumes, and what turns out not to be true, can be very damaging," he said.

A VMware spokesman said the company wouldn't provide details beyond what was in the blog post.

The company was also addressing upgrade issue via a Twitter account, vmwarefusion .