[CentOS] gpg decryption error from only 1 user

Hi all,
             I am having an issue. We have a vm that has encrypted data 
with gpg. The vm is centos 6.5 and it has multiple users. user1=bob 
user2=kevin user3= postgres user4=root. Only postgres has access to the 
file in which we keep the encrypted data. I as root will su - postgres, 
cd that data dir, and use this command "gpg -d (file_name)" and it works 
just fine. However the user1 "bob" will sudo su - postgres (have an 
entry in sudoers file to allow) and become postgres, cd to the dir with 
the data, run this same command "gpg -d (file_name) however it gives 
this error

gpg: CAST5 encrypted data
can't connect to `/home/postgres/.gnupg/S.gpg-agent': No such file or 
directory
gpg-agent[6153]: command get_passphrase failed: Operation cancelled
gpg: cancelled by user
gpg: encrypted with 1 passphrase
gpg: decryption failed: No secret key

I really do not understand whats going on here. I have tried deleting 
the user bob, and re creating it in case of some sort of corruption but 
still the same issue. We also see an issue where I installed screen. as 
any user but bob I can create or join. But as bob I get this error 
"Cannot open your terminal '/dev/pts/2' - please check."Also I, as 
superuser did this
su - bob
sudo su - postgres
cd data dir
gpg -d (file_name)

works with no issues, please help me debug this I am out of ideas.

thanks in advance