Still no dice. Now I'm checkpointing every 50 additions by calling "undef" on the index writer, and then reloading it. Once the index grows past a few checkpoints, I get:

Running checkpoint...
        (in cleanup) SIZE IS 0 at /usr/local/share/perl/5.8.4/Plucene/
+Index/SegmentTermEnum.pm line 74
        Plucene::Index::SegmentTermEnum::new('Plucene::Index::SegmentT
+ermEnum', 'Plucene::Store::InputStream=ARRAY(0x84a5ee8)', 'Plucene::I
+ndex::FieldInfos=HASH(0x872ce40)', 0) called at /usr/local/share/perl
+/5.8.4/Plucene/Index/TermInfosReader.pm line 52
        Plucene::Index::TermInfosReader::new('Plucene::Index::TermInfo
+sReader', '/tmp/swr8wHCzbm', '_55', 'Plucene::Index::FieldInfos=HASH(
+0x872ce40)') called at /usr/local/share/perl/5.8.4/Plucene/Index/Segm
+entReader.pm line 82
        Plucene::Index::SegmentReader::new('Plucene::Index::SegmentRea
+der', 'Plucene::Index::SegmentInfo=HASH(0x872d990)') called at /usr/l
+ocal/share/perl/5.8.4/Plucene/Index/Writer.pm line 274
        Plucene::Index::Writer::_merge_segments('Plucene::Index::Write
+r=HASH(0x84a75a4)', 5) called at /usr/local/share/perl/5.8.4/Plucene/
+Index/Writer.pm line 178
        Plucene::Index::Writer::_flush('Plucene::Index::Writer=HASH(0x
+84a75a4)') called at /usr/local/share/perl/5.8.4/Plucene/Index/Writer
+.pm line 119
        Plucene::Index::Writer::DESTROY('Plucene::Index::Writer=HASH(0
+x84a75a4)') called at ./updatedb line 86
        eval {...} called at ./updatedb line 86
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