Is it possible that LG or Verizon has put a limit of 1500 contacts on the address book? That's what I seem to be running up against for my Exchange account. Sync stops precisely at 1500. If I delete a few old contacts, and then resume sync, it stops again at 1500.
Called VZN, and ended up getting put through to an LG support person who kept telling me to upload my contacts to my Gmail account.