DeLorme released new firm ware back in Nov.2007 you might want to check any unit that pre-dates the release date to see if it is current.
Updated 11/26/2007
Article ID: 361
Earthmate® GPS PN-20 Firmware Update 1.3
The Earthmate GPS PN-20 Firmware version 1.3 updates the PN-20 as outlined in the release notes below. Download the update at the bottom of this page. This firmware update is available to DeLorme customers using either Topo USA® 6.0 PN edition or Topo USA 7.0. Improvements that only apply to Topo USA 7.0 users are noted in the list of enhancements.
Follow the link and you can see update.
http://www.delorme.com/support/supporttemplate.aspx?id=361P.S. Lloyd I do not think this release effects your unit because you obtained directly from DeLorme after the update.