Process error is my guess. I have used that a zillion times, just last week after rebuilding the primary control file because someone created the db with maxlogfiles=5, made new primary control file then create standby. Then 'copy' standby control file to other host and be sure its being used.

1) use an unusual name when you create it
2) verify it is transferred successfully
3) verify it is going in the right location by examining spfile