I did that, my batch file for troubleshooting was just
cgminer -o insertpoolhere.com -u username.1 -p password -I 11
This was with default clocking on the cards. When I raised the intensity to 13 I started getting hardware errors for both cards.
There is a known problem with some earlier motherboard PCI-e controllers and AMD cards so make sure that you add the
SETX GPU_MAX_ALLOC_PERCENT 100
SETX GPU_USE_SYNC_OBJECTS 1
commands in your command file or set them as system wide environment variables in Windows for ease.
If you still have problems then use the -d option and try each card individually as there could be a inconsistency between the two that causes the problem. It may mean that you have to run two instances of cgminer with slightly different settings, one for each card.