If you used a SD card some times ago, I don't think the SD slot is broken, I'd put it on the SD card !
If you have another one, as HarryT said, try it, if not, try 1. to format the SD card (completely, no fast format) in FAT32, and retry, or 2. to check for problems (right-click, Properties, Tools tab, I think - french version here
)
PS : I had issues with the upgrade too, due to my SD card. Didn't do anything when I pushed the nav button, didn't detect the card, I suppose. I had another one, so I tried it and it went well !