After dong lots of googling I figured out the answer myself. The E484 error in VIM refers to the case when Vim is unable to execute system level commands, like creating temp files, directories etc.
To check this run echo system("echo hello")
In my case I couldn't run this successfully. So I went through my _vimrc and found that somewhere I was setting set shell=/bin/bash
-> On a windows machine
After this the fix was simple. I just set the shell as
set shell=%System32%\cmd
Hope this helps anyone who is experience this kind of problem.