Ok done some more investigation.
Working on a clean VM Image of Windows 7 64 bit Ultimate Edition.
Initial install, AIS 5 works fine.
Next I remove AIS 5, add a 2nd HDD to the VM Image and create a Mirror Volume for the O/S drive, this in turn converts the disks to Dynamic Disks.
Allow disk to sync and then install AIS 5
Upon re-boot I now get a STOP error, UNMOUNTABLE_BOOT_VOLUME, booting into Safe Mode allows the system to boot and i can then remove AIS and get back to normal.
Definatley looks like AIS is changing something which stops a Dynamic Disk booting.
Any thoughts appreciated.
EDIT: For reference, this is a completley clean VM image today, not connected to the internet or even the local machine. Avast software was burnt to CD and trasnfered that way to ensure that the ONLY software to hit the VM image were Original Windows CD and then the Avast software - so no chance of getting a virus/trojan onto the system.