The drive issue isn't a 40GB issue, it has been happening with launch 60GB's too.
See this thread:
http://www.ps3forums.com/showthread.php?t=113728
On other news my 40GB did the exact same thing, it froze on Uncharted and after rebooting it won't read discs, the drive doesn't even spin up.
So it sounds like what was said on the PS3 forum, the drive controller must have shorted out.
Gonna get it replaced from a certain shop in a bit.