You most likely have a corrupted download. 7.1 GB is a large file, this is why network install was invented in the first place. I downloaded it via torrent.
Here is the head of my vbox installation log, a very basic install on my experimental server. The entire log is too large to post, but if your install is crashing at the very beginning your log is going to be none, or going to look very different from mine.
VirtualBox VM 4.3.20 r96996 linux.amd64 (Nov 21 2014 15:55:22) release log
00:00:00.887295 Log opened 2015-01-17T06:20:31.951658000Z
00:00:00.887296 Build Type: release
00:00:00.887298 OS Product: Linux
00:00:00.887299 OS Release: 3.13.0-43-generic
00:00:00.887299 OS Version: #72-Ubuntu SMP Mon Dec 8 19:35:06 UTC 2014
00:00:00.887313 DMI Product Name: ThinkServer TS140
00:00:00.887317 DMI Product Version: 70A4001LUX
00:00:00.887432 Host RAM: 15843MB total, 10266MB available
00:00:00.887434 Executable: /usr/lib/virtualbox/VirtualBox
00:00:00.887434 Process ID: 1249
00:00:00.887435 Package type: LINUX_64BITS_DEBIAN_7_0
00:00:00.921186 Installed Extension Packs:
00:00:00.921199 Oracle VM VirtualBox Extension Pack (Version: 4.3.20 r96996; VRDE Module: VBoxVRDP)
00:00:00.936796 UIMediumEnumerator: Medium-enumeration finished!
00:00:00.937106 Using XKB for keycode to scan code conversion
00:00:00.938619 SUP: Opened VMMR0.r0 (/usr/lib/virtualbox/VMMR0.r0) at 0xffffffffa1122020.
00:00:00.940886 Guest OS type: 'RedHat_64'
00:00:00.943064 fHMForced=true - Lots of RAM
00:00:00.943071 fHMForced=true - SMP
00:00:00.943075 fHMForced=true - 64-bit guest
00:00:00.946357 File system of '/media/abit/ISO/Lin/CentOS7/CentOS-7.0-1406-x86_64-Everything.iso' (DVD) is fuse
00:00:00.948904 File system of '/srv/VirtualBox_VMs/Experiment/CentOS7/Snapshots' (snapshots) is unknown
00:00:00.948912 File system of '/srv/VirtualBox_VMs/Experiment/CentOS7/CentOS7.vdi' is ext4
00:00:00.961183 Shared clipboard mode: Off
00:00:00.962319 Drag'n'drop mode: Off
For any and all install, if you do not have such list you might need to start one: what can and what cannot, affect a kernel (in your case it is the GNU/Linux, not Windows or Apple or BSD or HURD or any other) during boot, and during operation - for your hardware.
This is your own specific list tied to your specific hardware, as it is inconceivable to list all variations, or to spend anyone's time minding such data. Data, after all, do not equals (useful) information by proxy.
So far what I suspect in your case is that these are NOT suspects:
- The ISO
- The laptop's BIOS
- Xubuntu 14.10 plus all upgrades to date
- xfce and all updates to date
- Virtual Box 4.3.20 r96996
My experimental server's Xubuntu/xfce purpose is to host Virtual Box only, it is unchanged from the defaults except maybe the way I installed vbox - I only used the terminal, and I only used it once - what I currently have is no update or upgrade. I have not installed or removed anything else, what I do on this 'server' happens inside vbox clients, NOT on the host OS.
If you need to understand what is happening, one good approach might be to collect log data by the kernel, the distro, vbox and by client OS, and maybe more or better ways. This is a concept I am still trying to understand myself, so I end my update here. But I started to archive vbox client log data, and in time I would like to learn how to search and make sense out of them.