What's Wrong With My Glowlight Danio?!

[dvorak]

The other day I noticed a strange white bulge on one of my Glowlight Danios. It wasn't there the day before, but I have noticed this fish being loner. He tends to hide behind a tall rock we have and doesn't even come out to eat when i feed.
Also when he does swim around (usually in a little circle behind the rock) he swims slow and awkward, and kind of at a tilt, not straight up and quickly like the other Danios.
In the image it's right above his pectoral fin and right behind the gills.
http/img35.imageshack.us/img35/1717/img76542.jpg

Now a day later, the bulge is gone but now his under side looks funny.
http/img94.imageshack.us/img94/9238/img76722.jpg
http/img708.imageshack.us/img708/3856/img76812.jpg
http/img805.imageshack.us/img805/511/img76822.jpg