Stored Proc can't run psexec to remote server but SQLCMD mode can - help?

Question

I'm really hoping someone can help with my Access Denied issue issuing an xp_cmdshell "psexec" that otherwise works in SQLCMD Mode and the command line.  Any help would really be appreciated.
The setup:
Server 1.1.1.1:
I have a db MYDB (trustworthy, I'm an admin logging in using Windows Authentication)
I have psexec (running as admin, "everyone" has full-control from G:\
Server 1.1.2.1:
I have application ABC.exe (again, running as admin, "everyone" has full-control) on E:\Program Files
The problem
I can start ABC.exe from      1.1.1.1 from my command prompt for my user:
psexec.exe
\\1.1.2.1 -d -u DOMAIN\USER -p PASSWORD 
"E:\Program Files\ABC.exe" /accepteula
I can start ABC.exe from      1.1.1.1 from SSMS using the SQLCMD Mode:
!!G:\psexec.exe
\\1.1.2.1 -d -u DOMAIN\USER -p PASSWORD 
"E:\Program Files\ABC.exe" /accepteula
I
cannot get the command to run by      calling it from
a stored procedure or trigger:
EXEC xp_cmdshell 'G:\psexec.exe
\\1.1.2.1 -d -u DOMAIN\USER -p PASSWORD 
"E:\Program Files\ABC.exe" /accepteula'
I
cannot get ABC.exe to start on the      remote machine
by putting in the working command from #1 above into a batch file and calling that, either!
Thanks in advance,
Dave

Answer 1

OK, thanks. 
MORE INFORMATION: SQL is SQL 2012, two machines are WINDOWS SERVER 2012
I realize I'm probably treading in dangerous waters here, but I try to set the xp_cmdshell proxy account to two different users and I'm getting different results. 
Here's my two blocks of sql code:
GRANT EXECUTE ON xp_cmdshell TO [DOMAIN\user1]
EXEC xp_cmdshell 'whoami'
EXEC sp_xp_cmdshell_proxy_account 'DOMAIN\user1','pwd1'
EXECUTE AS login = 'DOMAIN\user1'
EXEC xp_cmdshell 'whoami'
EXEC xp_cmdshell 'G:\psexec.exe \\1.1.2.1 DOMAIN\user1 -p pwd1 "E:\Program Files\ABC.exe" /accepteula'
REVERT
GRANT EXECUTE ON xp_cmdshell TO [DOMAIN\user2]
exec xp_cmdshell 'whoami'
EXEC sp_xp_cmdshell_proxy_account 'DOMAIN\user2','pwd2'
EXECUTE AS login = 'DOMAIN\user2'
exec xp_cmdshell 'whoami'
EXEC xp_cmdshell 'G:\psexec.exe \\1.1.2.1 DOMAIN\user2 -p pwd2 "E:\Program Files\ABC.exe" /accepteula'
REVERT
And the results are (1) unexpected in terms of who the cmdshell user is and (2) the two executions are different failures:
Results from ALL the exec xp_cmdhell  'whoami' is DOMAIN\user3!
And the two different outputs (after both "Access is denied.") are
1 - Connecting to 1.1.2.1 ...                                                                           
Connecting to 1.1.2.1 ...
Couldn't access 1.1.2.1 :
and
2-Connecting to 1.1.2.1 ...
Connecting to 1.1.2.1 ...
Starting PsExec service on 1.1.2.1 ...
Could not start PsExec service on 1.1.2.1 :
I'm sure there's a clue in this output somewhere, it's just evading me.  I'm guessing there's something missing on the remote machine's security, but....