Sam,
You should have 3 groups with 2 members each.

You have that type of error because your redo log size is too small to handle the transaction
load.
what you need to do is re create your redo log with larger size.
before you drop your redo log make sure you only drop the redo log with INACTIVE status.

SQL>COL MEMBER FORMAT A40
SQL> select f.group#,
f.member,
g.status,
g.bytes bytes_mb
from v$logfile f, v$log g;

if they are active do the following.
SQL> alter system switch logfile;
SQL> alter database drop logfile group 1;
REM to delete logfiles from OS
SQL> HOST DEL C:\oracle\oradata\db_name\redo01.log

Also LOG_CHECKPOINT_INTERVAL = (set it larger than your redo log) and
LOG_CHECKPOINT_TIMEOUT=0. These 2 parameters influence how often your log switch.

Hope this help

Jean Richard.