Scheduled backups fail

I'm helping a friend with his Windows Vista PC and Acronis. After instralling, we ran a full backup to an external HDD and were able to retrieve files from this backup.

We then scheduled an incremental backup to run every 10 days (240 Hours). None of these ran over some months.

We then scheduled incremental backups to run every week on Mondays at 0900hrs. We did a run immediately of this task and it completed correctly and we could retireve files from the backup file. On the following Monday (11 October) there was again no scheduled backup file but he did get these messages:
At 9-02am Acronis Events Log showed 11th October 2010
New task back up operation started & in another box the following:
1 i information 100 2[0x640002]
2 i[in a yellow triangle] Warning 100 11[0x64000B]
3 i 1 information 506[0x 101FA]
4 i information 1 1,008 [0x103FO]
5 i Information 100 6[0x 640006]
ALL the information ones had the i after the number in a blue circle.

I've read the getting started message and downloaded the AcronisInfo Utility and Acronis Report exe to take to his place and try to sort out the problem.

Does anyone know what these messages indicate and what I should do to try and fix the problem of scheduled backups not running?