Satnav company TomTom is urgently working on a software fix after a number of its GPS models stopped working at the weekend due to a "leap year" bug.
The problem first emerged on 31 March when some users as far afield as the UK, Italy, Mexico, Switzerland, Denmark and Australia started reporting that their units couldn't get a fix from the GPS satellite system.
The company hasn't said which models have been affected by the big but said a temporary fix was possible if users reset their satnav units using instructions that vary by model.
"We have identified the root cause for some of our products not obtaining a GPS position," read a technical support message. "The issue is caused by a 'leap year' bug in the software of the GPS receiver. We are working hard on a permanent solution that we will make available on our website as a downloadable software fix."
The bug strikes when the GPS unit received signals from fewer than four satellites, the company said.
The reported symptoms vary, but typically involve the unit reporting a weak or lost signal, or displaying a grey screen with no data.
The company's support website logged approaching 400 messages of complaint from around the world by Tuesday, including some who said that even after the reset fix their units still worked very slowly. Others said that a reset only solved the issue until units were powered down, after which a further reset was required.
"Would be nice to be treated as knowledgeable adults. Again, I would appreciate if you would be honest and tell us what is going on," complained one user.
A full fix is promised for Tuesday or Wednesday 4 April.