External video card prevents liveUSB bootup

Question

External video card prevents liveUSB bootup Whenever I attempt to boot any Ubuntu liveUSB with a PCI video card installed, I see the initial ubuntu screen then it reverts to a text screen with the following errors:

BusyBox v1.13.3 (Ubuntu 1:1.13.3-1ubuntu11) built-in shell (ash)
Enter 'help' for a list of built-in commands.

{initramfs) mount: mounting /dev/loop0 on //filesystem.squashfs failed: Input/output error
Can not mount /dev/loop0 (/cdrom/casper/filesystem.sqyashfs) on //filesystem.squashfs
[  10.299584] sd 5:0:0:0: [sdb] Attached SCSI removable disk

Now if I take out the video card, it boots fine. But I don't want to use the onboard video port because it's defective with problems with shimmering & has low resolutions, etc.

I need to see how to this computer working with an external video card. The computer is a HP pavilion a815n with 2 gigs, and it's impossible to disable the onboard video in the bios.

I've tried with 4 different video cards from different manufacturers.

There's obviously a hardware conflict between ubuntu and any video card (memory contention?). No other pci cards are installed & all CD drives are disconnected.

I've tried different versions of ubuntu, from 10.04 thru 14.04. I used pendrivelinus universal USB installer to create the live usb (fat32 format), and they boot fine on all my computers but only on this one if no video card is installed.

Are there any boot options that may prevent the external graphics card from allowing the liveUSB to bootup?