I had the "no card" issue yesterday. The front screen showed "card inserted", but the menu indicated "no card".
As a side note, I had some difficulty during insertion of the 2 GB card, there was a small bit of plastic that was between a couple of the contacts that broke and was sticking up like a hang nail. I trimmed it off and thought all would be well.
I disassembled the UltiController and found this - Picture (a bent contact pin on the SD card slot). I was able to bend it back into place and it is, once again, working.
It was not necessary to remove the longer screws with the stand-offs that are holding the board to the wood cover. I removed the sides and the back only.
It has been mentioned that SDHC cards are not recommended for the Ultimaker UltiController. This may be the official recommendation, but I had been using 16 GB SDHC memry cards without an issue, except for the above (which is unrelated to the type of card).