Can't boot from USB, but could last night

[unckybob]

I recently purchased a ThinkPad Edge E420 and I am trying to install Ubuntu to it. I am trying to boot from an USB SDHC Card reader. I booted from it twice last night into the Ubuntu live desktop twice last night and it worked fine. Now it won't do it and I can't figure out why.

I tried selecting "Check disc for defects" and it said everything was okay.

1. Trying to boot from the USB card reader.

When I select "Try Ubuntu without installing", it leads me to a white text on black background screen which says:

BusyBox v1.18.4 (Ubuntu 1:1.18.4-2ubuntu2) built-in shell (ash)
Enter 'help' for a list of built-in commands.

(initramfs)

When I select "Install Ubuntu", it leads me to a white text on black background screen which says:

BusyBox v1.18.4 (Ubuntu 1:1.18.4-2ubuntu2) built-in shell (ash)
Enter 'help' for a list of built-in commands.

(initramfs) mount: mounting /dev/loop1 on /cow failed: Invalid argument
Can not mount /dev/loop1

2. Trying to boot from the internal card reader.

When I select "Try Ubuntu without installing" or "Install Ubuntu", it leads me to a white text on black background screen which says:

BusyBox v1.18.4 (Ubuntu 1:1.18.4-2ubuntu2) built-in shell (ash)
Enter 'help' for a list of built-in commands.

(initramfs) mount: mounting /dev/loop1 on /cow failed: Invalid argument
Can not mount /dev/loop1

Can someone pleas help?

[unckybob]

I just remembered that I used the "lock" slide on the side of the card last night before I put it away. I slid it to the "unlock" position and now it works just fine. I don't know why it worked, but I'm happy it did. If someone can explain why, I'd still like to know.

Perhaps it has something to do with the fact that it's a cheaper "no brand name" card. I got it cheap on eBay.

Thanks.