I may have fixed my problem by doing the following:
1. I installed a firewire card (800) into the server.
2. Plugged a external disk via the firewire 800 port.
3. moved the transactionlogs to the external drive. (i.e you to change your lotus notes transactionlogs settings.)
4. The do an full backup
5. then do incremental backup.
I have ran it for a week we no errors.
Issue seems to be it Transaction Logs are normally recommended to be on:
Raid 1/0
Separate Disk sub-system
Separate Controller
Hope this helps
Thanks
james