When I toured The Nielsen Company's $80-million, 475,000-square-foot data processing center in Oldsmar a few years ago, officials presented a facility poised to withstand just about anything the Tampa Bay area could dish out.

A fortified data collection area was built to endure a hurricane. Backup power generators were available to take over if Tampa Electric's power were interrupted. Tests had been performed to ensure lightning strikes would not disrupt service.

So how did a power transformer which blew out at 2:05 a.m. this morning, disrupt Nielsen's systems so badly that they could not release any ratings data today to clients?

"We have very good safeguards....but this was an unforeseeable, unprecedented event," said Nielsen spokesman Gary Holmes. "We don't even know all the information (about what happened)."

Holmes said a blown transformer sent a surge through Nielsen's systems which knocked out power at the Oldsmar complex. About 60 customers were affected by the outage, which lasted five hours; repair crews don't know yet what caused it, according to Tampa Electric Company. Nielsen's backup generators kicked in after an hour, Holmes said.

But the delay -- which occurred early in the morning, when Nielsen generally downloads data from thousands of households in its survey samples -- pushed back the company's process enough to scuttle overnight and weekly ratings reports to be released today. And officials can't say with certainty whether the data will be available tomorrow.

Nielsen took lots of criticism back in May, when computer server problems caused a delay in releasing ratings data for days, just as the networks were deciding on which series to keep for the next TV season.

 Then, in September, 14 heavyweight media companies united to create the Coalition for Innovative Media Measurement, an incubator for new techniques of audience measurement that some called a less-than-subtle challenge aimed at spurring Nielsen to work harder on new innovations.

With the economics of a multi-billion-dollar industry riding on its data processing abilities, Nielsen may face additional criticism -- particularly if the release of TV ratings is delayed by more than a day.