SSIS Packages Build Deploy Install Execute

1) When I first developed the packages, I was able to run build, deploy, install & execute them from command prompt.

2) From stored procedure I got error:
Error: 2006-10-24 14:58:54.62
Code: 0xC0016016
Source:  
Description: Failed to decrypt protected XML node "DTS:Password" with error 0x8009000B "Key not valid for use in specified state.". You may not be authorized to access this information. This error occurs when there is a cryptographic error. Verify that  the correct key is available.
End Error

3) Experts suggested to use package protection as Encrypt with password but still I could not succeed.

4) Now, we recreated the only package from which we kept password as before but while validation during install phase bottom 3 errors from below point 5) are reported.

5) Now from command prompt, I get following errors:
Error: 2006-10-29 22:31:07.72
   Code: 0xC0016016
   Source:
   Description: Failed to decrypt protected XML node "DTS:Password" with error 0x8009000B "Key not valid for use in specified state.". You may not be authorized to access this information. This error occurs when there is a cryptographic error. Verify that the correct key is available.
End Error

Error: 2006-10-29 22:31:07.94
   Code: 0xC0202009
   Source: pkgDept Connection manager "ISYS0221\ISPL001.IDB.sa"
   Description: An OLE DB error has occurred. Error code: 0x80040E4D.
An OLE DB record is available.  Source: "Microsoft SQL Native Client"  Hresult: 0x80040E4D  Description: "Communication link failure".
An OLE DB record is available.  Source: "Microsoft SQL Native Client"  Hresult: 0x80040E4D  Description: "TCP Provider: An existing connection was forcibly closed by the remote host.
".
An OLE DB record is available.  Source: "Microsoft SQL Native Client"  Hresult: 0x80040E4D  Description: "Login failed for user 'sa'.".
End Error
Error: 2006-10-29 22:31:07.94
   Code: 0xC020801C
   Source: Data Flow Task tblVarianceTransactionTypeSource [1]
   Description: The AcquireConnection method call to the connection manager "ISYS0221\ISPL001.IDB.sa" failed with error code 0xC0202009.
End Error
Error: 2006-10-29 22:31:07.94
   Code: 0xC0047017
   Source: Data Flow Task DTS.Pipeline
   Description: component "tblDept" (1) failed validation and returned error code 0xC020801C.
End Error

6) All this while right click on individual packages in solution explorer and it works fine.

Please suggest ways to overcome these errors and successfully execute my packages.