After warning that sales of its new GO product range were hit by the short-supply of a component during the second quarter, TomTom is now in danger of slipping behind its US rival Garmin.TomTom now predicts revenue will be 275m euros, a 10% sequential increase, though it said it’s gross margin for the quarter will be at least 40%. It also said, “Issues with respect to this component have been resolved and production levels are now satisfactory and in line with our planning.” Though it did not elaborate on the problem because it said it is in the quiet period prior to the release of its figures.Sales of portable navigation devices this year are expected to be between 3.6 million and 3.9 million units and revenue between 1.1bn and 1.3bn, 30% up on the 2005 figure, predicts Netherlands-based TomTom.