Error MongoDB - could not verify that config servers are in sync

Kindly let us know why we are getting the below error "config servers X.X.X.1:20001 and X.X.X.2:20002 differ" and "could not verify that config servers are in sync".

Errors are below:

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2014-12-03T09:25:43.412+0300 warning: config servers X.X.X.1:20001 and X.X.X.2:20002 differ
2014-12-03T09:25:43.414+0300 warning: config servers X.X.X.1:20001 and X.X.X.2:20002 differ
2014-12-03T09:25:43.415+0300 warning: config servers X.X.X.1:20001 and X.X.X.2:20002 differ
2014-12-03T09:25:43.417+0300 warning: config servers X.X.X.1:20001 and X.X.X.2:20002 differ
2014-12-03T09:25:43.417+0300 ERROR: could not verify that config servers are in sync :: caused by :: config servers X.X.X.1:20001 and X.X.X.2:20002 differ: { chunks: "d41d8cd98f00b204e9800998ecf8427e", databases: "37876c6920efc2704aa79ce9efe3f42e", shards: "01d69fd82221a9db33f2613ee52067b5", version: "6b9951b8fc5fdae808e728609d0e4e1f" } vs { chunks: "d41d8cd98f00b204e9800998ecf8427e", shards: "d41d8cd98f00b204e9800998ecf8427e", version: "47534b544a3d03c9726b3b58758892a7" }
2014-12-03T09:25:50.362+0300 [LockPinger] cluster X.X.X.1:20001,X.X.X.2:20002,X.X.X.3:20003 pinged successfully at Wed Dec  3 09:25:50 2014 by distributed lock pinger 'X.X.X.1:20001,X.X.X.2:20002,X.X.X.3:20003/KWTTSTMDBQRY001:27017:1417587823:1804289383', sleeping for 30000ms
2014-12-03T09:26:20.617+0300 [LockPinger] cluster X.X.X.1:20001,X.X.X.2:20002,X.X.X.3:20003 pinged successfully at Wed Dec  3 09:26:20 2014 by distributed lock pinger 'X.X.X.1:20001,X.X.X.2:20002,X.X.X.3:20003/KWTTSTMDBQRY001:27017:1417587823:1804289383', sleeping for 30000ms