Why my sdcard suddenly re-mount when phone in use to play game, watch movie or idle? I'm still newbie to android, I'm a little confused whether my android phone fine or damaged, or my sdcard is broken, because when I use the phone to play games, watch movies, or is in the idle position, sdcard suddenly unmount and then mount again (like doing re-mount). When running game or watch a movie suddenly close itself, and a notification appear "Preparing SD card". Anyone know why this could happen?

Here my phone information : 

RAM : 256MB, ROM : 256MB, Model number: Device-01, Android Version: 2.3.6, baseband version: VENUS_BP_00.03.63.b501, Kernel Version: 2.6.38.6-perf zly @ HL120 # 1

My sdcard : V-Gen 2GB.

Thank you.
sdcards remount by default as read only on errors, could be one.

or the contacts of the sd slot are dirty or loose

or the micro usb port is so overused that random connect events happen that might get your card unmounted for a mount on a then not existing pc.

^that paragraph

is based on what happened to my motorola milestone 2, if I plugged that into the car charger it want crazy activating and deactiving dock mode 6 times per second.
maybe something similar goes for charge indicatiors.

also magnets in vicinity of androids can cause the strangest quirks