It was after deploying a newly created application and during starting the application got following error
"Microsoft.Xlangs.Core.ServiceCreationException:Failed while creating ApplicationNameClient service."
Why it happened
The development environment comprises of two BizTalk servers in same group. On one of the box(dev machine1) I deployed the application and used one of Host Instance whose Host was on another dev box(dev machine2).
When tried starting the application got error-- it was because the host instance didn't find the assembly in the GAC.
It made sense as I have deployed the application on Biztalk Dev Machine 1 and GAC of this machine has that assembly whereas GAC of BizTalk Dev machine 2 does not have it thus host instance of machine 2 couldn't find it and thus the error.
What to do
1. I choose to use host instance of BizTalk Dev machine 1 itself
2. In case you need to use BizTalk Dev machine 2 host instance then add the assembly in GAC of that machine
3. And off course restart the host instances 
