I had a different problem this morning. Running Windows 7 (32-bit), and my laptop has a built-in reader for SD cards. Put the card in the slot and LR3B2 (is it just me or is Adobe approaching Canon in the names department?) launched. I have 'eject card after import' selected, and it imported the images just fine and 'ejected' the card. It also disabled the card reader completely. I haven't done so yet, but I'm assuming rebooting the computer will re-enable it. Right now even Windows Explorer won't acknowledge that there's a card in there. I'm going to post this on the LR bug report form when I get a moment.
Mike.
Update:
Shutting down/ restarting solved the problem, but there's more. I also have a USB reader for my desktop, so I tried the same SD card with that - worked fine. Undaunted, I put the SD card back in the integral reader and it also worked fine. After some head scratching I remembered that I had updated to Firefox 3.62 last night, so - MAYBE - there was a conflict that affected the device driver that shutting down and/or re-reading the registry fixed. Nothing worse than an intermittent problem. I posted this on the LR Forums at Adobe - there are others there having import problems so you may want to read there.