CPU: AMD Athlon 64 X2 4800+
MB: MSI K9VGM-V
GPU: Leadtek GeForce 8400GS 256MB
2gb RAM
80gb HDD

I've installed 10.5.2 to a newly-formatted HDD and after the installation, when I try to boot into Mac, a 'No-Entry' symbol appears on the load screen. Screenshot:
http://img167.imageshack.us/img167/3152/spa0152nm6.jpg

I managed to get 10.5.1 working almost-perfectly and have not seen this error before. Does anyone know what could be causing it?
Thanks.