Why does "Preparing SD card" message appear on Optimus One P500 3-4 times a day? On my Optimus One P500 it shows.

Preparing SD card


The above message shows at least 3 to 4 times in a day.

During this Apps on SD cards are automatically closed.
Any files opened(Music/PDF) as not accesible.

Is this a issue with me or Optimus or android 2.2
I had a similar problem that was fixed by formating the card in the phone. 

Settings -> SD card &amp; phone storage settings -> Unmount SD card. Then format the card on the same screen.