VolSnap Error Messages in Event Log

I have Acronis True Image 10.0. My PC is running XP Pro. I have a 500 GB hard drive, and 4GB of memory, with a fast processor.

I have scheduled two backups to run at night. I am backing up my C drive which uses about 49 GB of the drive.

1. An incremental backup of the entire C drive. Runs at 2 AM, saved to the D partition on the same drive

2. An incremental backup of certain folders on the C drive. Runs at 3.30 AM, saved to an external USB drive

In the morning, the PC is locked up and needs a reboot. I am getting the following error message in the events log:

The shadow copy of volume G: could not be created due to insufficient non-paged memory pool for a bitmap structure.

The shadow copy of volume G: became low on diff area space before it was properly installed. (Volume G is an HP Simple Save USB drive. It is 1TB)

The shadow copy of volume G: was aborted because the diff area file could not grow in time. Consider reducing the IO load on this system to avoid this problem in the future.

Again, volume G is the HP Simple Save 1TB USB drive

Suggestions?

Thanks!