1. make sure you're using a 64-bit OS
2. make sure your memory is on the compatibility listhttp://global.shuttle.com/support_list03.jsp?PI=1219
If not, return it and have it replaced.
3. If you have a low-wattage video card available, try replacing your GT240 to see if you have a power problem.
4. Get in touch with Shuttle support.
5. Otherwise RMA the barebones box.