After I changed my card from a class 10 Adata brand 8 G card to a Class 4 Super Talent brand 8 G card, the SD card problem seemed dissapeared. This may expalain why some people got the problem but others not - NOT all cards are workable under firmware 1.9.11. But how to find a workable card? Try as many as you can until you find one.
This simple reader has been kept giving me little troubles that move me away from focusing on reading since day one. Good thing is that Kobo has been trying to fix them through firmware upgrades. But, Hey, KOBO, please do not create new bugs while solving the existing ones.
A thing still bugs me is that the bottom line of a Pdf page is often cut off, which never shows on Sony's PRS-950 or Amazon Kindle or Astak EZreader Pro.