Cannot process Cash Book entries

Good day,

I really need serious help on this Overdraft thing. I am working in my current set of accounts for 2012 - I do a daily cash book and never once had an issue with errors. Now I have over 11,000 in the bank and doing a 4,045 transaction and I am STILL getting this - The bank transaction would result in exceed of authorized overdraft limit for transaction: # on . - ERROR.
Surely you can see by now it is NOT an issue of having lack of funds but there is a serious problem here. In the 6 months i've been using FrontAccounting processing numerous cash books it has never given these errors until now.
Can someone please HELP?