1. Try opening the File > Tournament Results - Manual Entry > PokerStars window. Scroll through the top left data section. As you do, in the bottom left section it will display the results which includes the number of players in the tourney. Look for large tournaments (more than 1000 players?) and use the "Delete Players w/ No Hands Loaded or Winnings" button. Once you do that, open the Utilities > Database Maintenance and Options window and use the Purge Players button (even though it's on the ring tab, it will still remove tourney player names) and then finally do another full v/a and try to import again.
2. Going forward, use the Customize Summary Info. to Import button on this window to have PT limit the number of names that it imports to just those players that won money or that won money and you played against.