I am having a somewhat similar issue well kinda it seems to me that ubuntu is not finding my hard drive when I am attempting to install ubuntu. it gets to the busybox promt, then displays (initramfs) and hangs I know the cd and my hardware are good I ussually run this as a windows box I'm new to linux so I thought I would try this on a diff HD after playing with it some in a VMWare machine inside windows. LIke I said I have used the Ubuntu DVD From Ubuntu b4 to load it in a VM and all My hardware works fine in windows.

below is a hardware list any help would be greatly appriciated-

XFX Nvidia 750a SLI Mobo
AMD Phenom 8650
4GB PC2 6400
80GB Seagoate Berracuda Sata Drive
1 IDE DVD Burner
1 SAta DVD Burner
Nvidia 9800 GT Video Card
6 Port USB Expansion card (PCI)
13-1 Media Card Reader

I have disconnected all other hardware including the media card reader to no avail