To further elaborate on Yehuda's twit:

[~/tmp][rando@apollo]
 % mkdir first first/second
[~/tmp][rando@apollo]
 % touch first/second/test.txt
[~/tmp][rando@apollo]
 % chmod -x first
[~/tmp][rando@apollo]
 % ls first/second/*.txt
ls: cannot access first/second/*.txt: Permission denied
[~/tmp][rando@apollo]
 % irb
irb(main):001:0> Dir.glob('first/second/*.txt')
=> []

If you try to glob some things in a directory that has some ancestor missing the eXecute permission, ruby doesn't give any indication of an error.

This took Yehuda and I about 30 minutes to track down why a merb app wasn't loading bundled gems under passenger. Apache was running as nobody, and the parent dir of the app was missing the global execute permission.