DIF occurance not getting created

Hi experts,

We use correction DIF in Forecasting and Replenishment module while generating forecast. From last one week when we just hit enter after selecting the DIF ID = COR (happens with any other DIF ID). the information message is pooped up: '0000000254 already exists'. If you go to the /FRE/DIF_OCCURR table, you will see that the DIFN 254 does not exist. Also does not seems an authorization-check problem. Also checked if there was some table locking and there was no locking. So not sure how to correct this.

Thanks & Regards

Yogeesha