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.