Here is a description of the new update… Hope that helps
>>> Software Update Notification (June 5, 2009): Following the release of HDS Update 2.0.30.50 on May 15, 2009, field reports indicated a concern with HDS units not reading select U.S. lake maps on a limited number of Navionics charts. Specifically, the problem is known to affect portions of lake maps on Navionics HotMaps Premium North and HotMaps Premium East 2009 charts.
Now available for download, this more recent HDS software release — 2.1.30.58 — corrects the limited number of concerns previously experienced with 2.0.30.50 (as noted above). In addition, this latest HDS software update will also dramatically increase the speed of loading times for all Lowrance cartography. <<<