Like many of today's cars, not even the Segway Personal Transporter is immune from its own set of problems that lead to recalls. The company announced in cooperation with the U.S. Consumer Product Safety Commission a voluntary recall to upgrade the software in the units to prevent users from falling off in certain circumstances.

Although the company has highlighted that it is nearly impossible to fall off the Segway, it has been documented. Shortly after its launch, President Bush took a tumble off a Segway while testing out the unit, raising questions as to its safety. However, Segway clarified to BetaNews that the President had forgotten to turn on the transporter before attempting to use it.

While it is not clear if any specific incidents prompted the recall, Segway is asking users to contact the company to register for the free upgrade.

Segway said the condition has been identified within the PT i Series, e Series, p Series, XT, GT and i2 models. The X2 model due out later this month is not affected, and the i2 comes shipped with the software update installed.

According to the recall, an unexpected reversal of direction can cause the rider to fall off the unit. It is said to occur when the units speed limiter tilts the Segway to slow it down, and the rider goes off and back onto the unit within a short period of time.

"The safety of our customers and our products is our top priority. When we identified this condition we notified the CPSC and immediately began working on a software upgrade to address the issue," Segway CEO Jim Norrod said in a statement. "We are committed to making the upgrade process convenient for our customers."

Segway PT owners should contact the company at 800-750-6557 between 8 a.m. and 8 p.m. ET, Monday through Friday, or visit the Segway Web site to register for a free software upgrade, the company said.