if I recall correctly, Illustrator couldn't snap guides to text boxes in CS6.
Snapping in general was terrible in CS6. It was especially annoying.
You may be able to do it with the Direct Selection tool, snapping it to a corner anchor.
If not, there is a workaround! You can use Align to Key Object to do the same thing.
If you're unfamiliar with it, here's how to do it...
Using the Selection tool, select the text box and the guide you want to align along the left side
Now, click on the selected text box. The selection outline should get slightly bolder.
Now, in the alignment tools on the to menu (or in Align tool panel, or in the Align section
of the Preferences tool panel) click on the "Horizontal Align Left" button.
It kinda looks like this:
Repeat for any other guides you need.
