ERROR:
Unable to start execution of step 1 (reason: Error authenticating proxy DOMAIN\USER, system error: ConnGetProxyPassword). The step failed.
EXPLANATION:
I encountered this error when running a Job. The error occurred when the SSIS package in Job was run with a Proxy. The proxy account is also using a Credential, and the problem was due to an incorrect password definition for the user in the Credential definition.
SOLUTION:
Make sure that the appropriate Credential settings are correct. Make sure that the user information you are using is correct.