Nero BackItUp Error

Hello Gurus:

I am using Nero BackItUp ver 1.2.
I have been running incremental backups fine for about a month now, but today when I tried to do the incremental to the DVD in which I just made a Full Backup, I keep getting the error message

"Backup information file could not be opened"

There is no further explanation given. So I do not know what could be wrong.
Please let me know what you think. Thank You.

My PC is a Pentium 4, 3.2GHZ
1GB of RAM.
O/S: Win XP Home SP2