mongoose: Please help.. I get process.nextTick(function() { throw err; })

Versions I am using

Ubuntu 14.04
MongoDB 3.0.1 with --storageEngine wiredtiger enabled
Mongoose 4.0.1
Node JS 0.12.2

My Dev environment is Mac and everything works good. I pointed my dev environment to live mongoDB and it works.

But when I try the same in my staging with the above versions I get the below error after a while.

/home/ShopWaveServices/api/Up/CoreDB/node_modules/mongoose/node_modules/mongodb/lib/server.js:228
        process.nextTick(function() { throw err; })
                                            ^
Error
    at Object.<anonymous> (/home/ShopWaveServices/api/Up/CoreDB/node_modules/mongoose/node_modules/mongodb/node_modules/mongodb-core/lib/error.js:42:24)
    at Module._compile (module.js:460:26)
    at Object.Module._extensions..js (module.js:478:10)
    at Module.load (module.js:355:32)
    at Function.Module._load (module.js:310:12)
    at Module.require (module.js:365:17)
    at require (module.js:384:17)
    at Object.<anonymous> (/home/ShopWaveServices/api/Up/CoreDB/node_modules/mongoose/node_modules/mongodb/node_modules/mongodb-core/index.js:2:17)
    at Module._compile (module.js:460:26)
    at Object.Module._extensions..js (module.js:478:10)

Please help.

I tried setting up auth in mongod, Ports are open for all the required IP addresses.

Please help me fix this.

Many thanks, Karthik