'Transfer Cancelled' Why does this occur

I run an SMSF account with Reckon’s software and I quite often execute share trades. I did so two days ago, but when I subsequently tried to add to, and delete shares from, my SMSF account I received the following error message: ‘transfer cancelled’. So, I gather that I can no longer add or delete share-holdings from the Reckon file dealing with the SMSF. However, and this is very strange, I can add and delete shares other share-trading accounts. So why is there a problem with the SMSF file? Could it be that the file, which has been running for well over a decade has now exceeded a maximum size? This, however, seems unlikely as I can update share prices daily.