Sporadic failures of 'resolve_conflicts_dropped_modified_1'

On running the test suite the last few weeks on several
revisions I've had 'resolve_conflicts_dropped_modified_1'
report success and 3 identical failures but from 3 different
lines (line 130, line 149 and line 208) but *all of these
results* are for any single of the tested revisions.

Examining the core file in NetBeans shows the revision_id
passed to 'get_revision_parents' as an empty string.

Any thoughts?

ps. All other tests pass every single time.

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Program terminated with signal 11, Segmentation fault.
#0  0x0807eddc in boost::detail::sp_counted_base::add_ref_copy (this=0x20) at /usr/include/boost/detail/sp_counted_base_nt.hpp:65
65	        ++use_count_;
(gdb) bt
#0  0x0807eddc in boost::detail::sp_counted_base::add_ref_copy (this=0x20) at /usr/include/boost/detail/sp_counted_base_nt.hpp:65
#1  0x0807ee1e in boost::detail::shared_count::shared_count (this=0xbf8ec618, r=...) at /usr/include/boost/detail/shared_count.hpp:227
#2  0x0807ef68 in boost::shared_ptr<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >::shared_ptr (this=0xbf8ec614)
    at /usr/include/boost/shared_ptr.hpp:165
#3  0x0807ef82 in immutable_string::immutable_string (this=0xbf8ec614) at src/vocab.hh:28
#4  0x0807302e in id::id (this=0xbf8ec610, other=...) at src/vocab_terms.hh:18
#5  0x0807f5b0 in revision<id>::revision (this=0xbf8ec610, other=...) at src/vocab_terms.hh:57
#6  0x081e839e in database::get_revision_parents (this=0xbf8ecbf4, id=..., parents=...) at src/database.cc:2690
#7  0x083afeae in content_merge_database_adaptor::get_dropped_details (this=0xbf8ecad8, rev_id=..., nid=2, dropped_rev_id=..., dropped_name=..., 
    dropped_file_id=...) at src/merge_content.cc:209
#8  0x0839bce6 in push_dropped_details (db_adaptor=..., rev_sym=..., name_sym=..., file_id_sym=..., rev_id=..., nid=2, st=...)
    at src/merge_conflict.cc:1076
#9  0x0839f0a0 in roster_merge_result::report_dropped_modified_conflicts (this=0xbf8ecea8, left_roster=..., right_roster=..., adaptor=..., 
    basic_io=true, output=...) at src/merge_conflict.cc:1187
#10 0x083a982d in roster_merge_result::write_conflict_file (this=0xbf8ecea8, db=..., lua=..., file_name=..., ancestor_rid=..., left_rid=..., 
    right_rid=..., left_roster=..., left_marking=..., right_roster=..., right_marking=...) at src/merge_conflict.cc:2688
#11 0x0819580a in conflicts_t::write (this=0xbf8ecea8, db=..., lua=..., file=...) at src/cmd_conflicts.cc:46
#12 0x0818f75d in commands::cmd_resolve_first::exec (this=0x85729a0, app=..., execid=..., args=...) at src/cmd_conflicts.cc:797
#13 0x080da019 in commands::process (app=..., ident=..., args=...) at src/cmd.cc:224
#14 0x08419067 in cpp_main (argc=14, argv=0xbf8ed684) at src/monotone.cc:294
#15 0x0841971c in main (argc=14, argv=0xbf8ed684) at src/unix/main.cc:148
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