XPS 420 Intel Raid Driver Prevents Sleep in Vista

I have an XPS 420 which I purchased in June 2008. It has a mirrored raid hard disk drive (2x512GB). Whenever I try to put my pc to sleep, I get a System Standby Failed error message "The device driver for the 'Intel(R) ICH8R/ICH9R/ICH10R/DO SATA RAID Controller' device is preventing the machine from entering standby. Please close all applications and try again. If the problem persistes, you may need to update this driver". I followed the advice and updated the controller to version 8.5.0.1032 from the Intel site. However this does not solve the problem and I still get the error message. The raid controller icon appears in my notification area after startup and is generally flashing most of the time as the volumes are verified. It appears to continue verifying/checking constantly and takes many hours to complete. The Matrix Storage Console indicates the drives are OK. How can I enable the driver to allow sleep/standby mode? Is this a limitation of RAID? Any assistance would be much appreciated.

Sulakhan