I moved this as I don't think it is related...
Can you open Lightroom at all??? look in the folder where the catalog is (with Lightroom closed) and if there is a file ending with .lock, remove this.
Yes I can run LR5 alright, and by selecting Import I know it isn't proceeding through the Import process.
I found an old .lock file, latest modify date was last year. I closed LR and deleted it but still no sign of Import happening. All I see is a small circular progress display spinning in the lower left corner after I select a camera source first time in the Import screen, but it stops after a second or two.
What happens when you try to import?
Describe in detail.
Quote any error message completely and exactly.
Unfortunately there are no further details to describe. I should say were since the problem has gone away I now see (I was going to get a screen shot).
It may be that after rebooting a few times for this and routine reasons I neglected to reboot after deleting that old .lock file. That's all I can think of, though it was not a recent file so it seemed unrelated.
For the record though, here's all that happened. LR5 ran in its image browser mode as normal. I used the Import button to invoke the Import dialogue. My camera was displayed along with folders I could select. I clicked on the camera, a button with "D90" in it. A small worm-like animated gif displayed tracing a circle low and on the left and then stopped, it froze, after about two seconds, then cleared. If I tried to select a folder I knew had jpegs in it, or clicked the camera again, the gif did not redisplay. So as far as feedback in this situation, LR gave me just that gif!
(Bear in mind the title of this thread is from the OP. In my case as I said I plug in cameras rather than cards and then select them.)
Thanks for all your suggestions.
Try importing from the card and a reader as opposed to the USB cable or try another cable as well.
I have had the problem of disappearing import sources using Windows 7 64-bit. Your problem describes the symptoms very well. Microsoft has a fix for this problem using the Fix-It facility. Go here and click Run Now.