Warlord Ajer'laroir, I advise reading the patch notes to see what has been changed. Next to the removal of map protection, alteration of the syntax checker and some bug fixes not much has changed.
daverave1212, if it is your map using offical WE (not third party modifications to WE) and it saved without error with no imports, what you are reporting should never happen.
If you are using a third party editor modification, try asking the makers as unfortunatly that is not a usual error.
If you have imports, try removing all for a test of them as they can cause bugs to arise while saving.
World editor must be left to save completly and shutdown properly, sudden power outages, closure while saving or inceficient privaladges will result in an incomplete (curropted) save. Additionally if you have set your backing storage drivers to respond buffered writes as completed writes (this is almost always turned off for safety) then it might be data curroption caused by the writing to the disk failing to complete.
Level data refers to the group of files stored in the MPQ which contains the doodad, destructable and terrain type placements. The name probably is reminence of early designes where WC3 was being considered as an RPG.