LG Optimus S / Optimus U / Optimus V
preparing sd card and spontaneous reboots
All 3 say "preparing SD card" several times a day (at least). I tried a 2gb sandisk sd card instead of the samsung 2gb card that comes with it - same thing. Apps installed to the sd card disappear from the apps menu then mysteriously reappear. Also shortcuts on the main screen change to a default icon then may change back when they feel like it.
Also getting spontaneous reboots - not sure if this is related to the sd card issue.
Will likely return these before the 30 day period is over.
Go to the SD menu, unmount the card, format, then re mount it. That should fix it!
Be sure to backup stuff on your computer first.
If that doesn't work, then get another SD card, even an old one, and do that same process with the new card.
I had the same problems and have not had it since I did this.