Backup ends with error-Help, please!

I have 2 disks on my system and backup opn a daily incremental basis. Disk C goes OK but Disk D, after some weeks of being OK, now ends with an error - 0x000B03EC. I went to the Acronis KB and found a suggested way to deal with the problem but when I right click on the failed backup, I don't get the entry 'Remove from the List' as suggested; and I did look on the 'more' menu.

So are there any ideas for going forwards with this problem? And why does it arise in the first place - does anyone know?

Thanks

Alan Willmott