Assuming you have a real 128 MB Smartmedia card, you can try re-formatting the card in the eBookwise reader itself. As this will wipe out your card, please ensure you have a backup copy of each ebook in your reader.
Only try this if it is your only choice!
Please follow these instructions and don't stray:
1. Turn off the eBookwise 1150 reader.
2. Hold the bottom page button down.
3. While holding the bottom page button down, turn on the unit.
4. You will notice a message at the top "Arranging your Bookshelf..."
5. At your eBookself page, touch the top-left icon (off-screen; it looks like a person holding a book) to bring up the menu that begins with 'Info'.
6. Tap the 'Info' icon and confirm you see your Name and User ID.
7. Tap the 'more' icon there.
8. Tap the second 'more' icon that just appeared.
9. Tap the 'erase external' icon to reformat the 128 MB card that you have in.
10. If and only if you have backups of your ebooks, tap the 'Yes' icon and wait for it to finish formatting the card.
11. Turn off the unit!
12. Turn on the unit normally.
13. Tap the 'bookshelf' icon above your eBookshelf and confirm your MB and % free of 128 MB.
Hope this helps.