To return to your original problem (in case it reoccurs):
I've had similar problems with that 'loading' line hanging when I've my computer has experienced problems reading from removable media. Given that the problem occurs for you with different SD cards (and that they work elsewhere) my guess is that your card reader is about to pack up. (I've had built-in card readers fail on several computers).
So, if you experience the problem again, I suggest trying the SD cards in a USB card reader (instead of your built-in one). They're not expensive!
http://www.poundland.co.uk/signalex-multislot-card-reader-assorted