Garmin has issued an alert (PDF file) warning owners of recently delivered new and repaired GPS units not to use them for DME arc procedures. The main software (versions 5.03 and 4.03) installed in Garmin 500- and 400-series units shipped new or shipped after repair between Feb. 11 and March 2 apparently has glitches that could give incorrect navigational information and/or an incorrect depiction on the moving map display while flying DME arc procedures. The immediate fix is to revert to the previous software package, which lacks features of the new program. New full-feature corrected software should be available by March 31. The alert asks pilots to spread the word about the problems and to immediately contact a Garmin Service Center for instructions on how to fix the problem. The affected units are those shipped between Feb. 11 and Mar. 2 and include: GNS 530, GNS 530 TAWS, GNS 530A, GNS 530A TAWS, GPS 500 and GPS 500 TAWS with main software version 5.03. Also affected are GNS 430, GNS 430A, GNC 420, GNC 420A and GPS 400 units with main software version 4.03.