TomTom sat-nav devices hit by GPS 'leap year bug'
TomTom has blamed a "leap year bug" for a fault causing some of its satellite navigation devices to malfunction.
The firm said that a problem with its global positioning system firmware - code embedded into the devices - was causing"a limited number of models"to fail to identify their location.
Affected users are presented with a grey screen and a message saying the machine lacks a GPS signal.
The firm said that it was working on a fix and promised further updates.
The Dutch company said that the issue first emerged on 31 March.
It suggested that customers should reset their devices by holding the on/off button down for 20 seconds, saying the move acted as a temporary fix.
TomTom told the BBC that it would "update customers on which models are affected as soon as we know more".
The problem appears to affect devices worldwide, with users in the UK, Australia, Switzerland and Denmark among those complaining of the problem.
One user of the firm's Go Live 1005 model told the BBC that he had encountered the problem on Sunday during a trip from Gatwick Airport to Cornwall.
"It refused to shift its position from Gatwick and kept showing a message saying 'looking for valid GPS signals,'" Graham Pitt said.
"I assumed it had broken but when I went to check TomTom's website I saw there were similar complaints about a range of models on its discussion boards. I feel this should have been made public earlier to alert customers to the problem."
A thread titled "No GPS Signal"on TomTom's site had attracted more than 350 posts by Tuesday afternoon.
A statement from the firm said: "Please accept our sincere apologies for the inconvenience caused."