Do use the code Hurrian gave you, if you have the package 'sudser' installed.
If you have rootsh installed do http://talk.maemo.org/showpost.php?p...93&postcount=2

You better have one of them installed to get your data back.

If, however, you have no data, that is important for you the easiest is to format the card from the Hildon File Manager. But you better be sure to not lose any data in this process.