Default SD card damaged on reboot for no reason :(

I have rooted MK2 but no Safestrap/roms. The last thing I updated was Titanium backup, a couple days ago.

Today, everything was great until I rebooted my phone to see if I could get better wifi reception at work, and suddenly my sd card is corrupted! for no reason! I had a ton of stuff on there, included all my backups

has anyone else had this issue? is there anything I can do to prevent this happening again?