Newbie problem with startup: ORA-16038 -> ORA-19504 -> ORA-19504

I'm new to Oracle and this community support forum, so pardon me if this isn't the right place for this.

I'm unable to open a recently installed database (11g) and am getting these errors:

SQL> alter database open;  
alter database open
*
ERROR at line 1:
ORA-16038: log 2 sequence# 80 cannot be archived
ORA-19504: failed to create file ""
ORA-00312: online log 2 thread 1: '/u02/oradata/cidrap/redo02.log'

The second line puzzles me -- failed to create file ""

What's the missing file that it's failed to create?  The file listed in the underlying error exists and is time-stamped with a very current time (within 20 minutes as of this moment) so it seems like that's not the one it failed to create.