I have noticed in that past 24 hours that two rigid and straight "lines" have developed as bulges on my Mid 2010 MacBook Pro 15 inch.
They are noticeable when looking at it in the light and you can easily feel that they are raised above the case.
They appear on the outer shell of the case (right of the mouse and near the keyboard)
The bottom of the Mac is not warped. The hard drive also appears to be in good condition.
Initially, I thought this was due to a battery failure and removed the battery. Despite this, the battery was fine (not warped or bulging). I noticed that the two bulges in the case appear over where the hard drive is in a MacBook Pro.
There is also a "semi circular" bulge near these two lines.
What could be causing these if it is not the battery? Also, is there any chance that these bulges could expand?
Edit: After further inspection it appears to have occurred exactly over the bridge that holds the hard drive in place. (the long black piece with the two screws in it).
I have added a picture. Sorry, they are really hard to see.
Note: The two lines look like shadows and are somewhat difficult to see in (any) photo.
Edit: more photos
The second image (below) shows what is under the bulge. Maybe something looks out of place?