One click to clean out date property!
Just make sure the Waypoint Date Field in HBPC is not blank, or HBPC will give a date data error during file open. Then the GPX file is corrupt to HBPC. One such Waypoint will do this.
This is a BAD, VERY BAD HumminbirdPC 4.3.8 long ago reported bug. <------GREG read this!!!!!!!!!!!!!
One quick fix is to perform a HBPC upload to a SD-card, then just download back into HBPC.