This bug and all of its duplicates seem to have happened during a distribution upgrade:
LP: #930839 has a total of 12 duplicates
UpgradeStatusLP: #930839 has a total of 12 duplicates
UpgradeStatus
[3] Upgraded to precise on 2012-02-11 (0 days ago): 930558, 930661, 930923
[2] Upgraded to precise on 2012-02-10 (0 days ago): 930163, 930356
[1] Upgraded to precise on 2012-02-17 (0 days ago): 934340
[3] Upgraded to precise on 2012-02-13 (0 days ago): 931198, 931616, 931671
[1] Upgraded to precise on 2012-02-14 (0 days ago): 932015
[1] Upgraded to precise on 2012-02-12 (1 days ago): 931292
[1] Upgraded to precise on 2012-02-12 (0 days ago): 931011
[3] Upgraded to precise on 2012-02-11 (0 days ago): 930558, 930661, 930923
[2] Upgraded to precise on 2012-02-10 (0 days ago): 930163, 930356
[1] Upgraded to precise on 2012-02-17 (0 days ago): 934340
[3] Upgraded to precise on 2012-02-13 (0 days ago): 931198, 931616, 931671
[1] Upgraded to precise on 2012-02-14 (0 days ago): 932015
[1] Upgraded to precise on 2012-02-12 (1 days ago): 931292
[1] Upgraded to precise on 2012-02-12 (0 days ago): 931011
This bug and all of its duplicates seem to have happened during a distribution upgrade:
LP: #930839 has a total of 12 duplicates
UpgradeStatusLP: #930839 has a total of 12 duplicates
UpgradeStatus
[3] Upgraded to precise on 2012-02-11 (0 days ago): 930558, 930661, 930923
[2] Upgraded to precise on 2012-02-10 (0 days ago): 930163, 930356
[1] Upgraded to precise on 2012-02-17 (0 days ago): 934340
[3] Upgraded to precise on 2012-02-13 (0 days ago): 931198, 931616, 931671
[1] Upgraded to precise on 2012-02-14 (0 days ago): 932015
[1] Upgraded to precise on 2012-02-12 (1 days ago): 931292
[1] Upgraded to precise on 2012-02-12 (0 days ago): 931011
[3] Upgraded to precise on 2012-02-11 (0 days ago): 930558, 930661, 930923
[2] Upgraded to precise on 2012-02-10 (0 days ago): 930163, 930356
[1] Upgraded to precise on 2012-02-17 (0 days ago): 934340
[3] Upgraded to precise on 2012-02-13 (0 days ago): 931198, 931616, 931671
[1] Upgraded to precise on 2012-02-14 (0 days ago): 932015
[1] Upgraded to precise on 2012-02-12 (1 days ago): 931292
[1] Upgraded to precise on 2012-02-12 (0 days ago): 931011