Hello Andrew
It is not possible to post any entries without reversing the Balance Carry Forward. You just need to reverse the Step 2 of the Balance Carry forward and then you post the entries. After that you can again execute the Step 2 of the Balance Carry Forward run.
You need to re-open the Fiscal Year and last period of the year 2013 to reverse the Step 2 of the Balance Carry forward run. In case you are still unable to reverse it,kindly let me the exact error message you receive while reversing the Balance carry forward run.
Thanks
Parveen Kumar