This is what happens sometimes during a gem install:
Successfully installed json_pure-1.2.0
Successfully installed rubyforge-2.0.3
Successfully installed hoe-2.3.3
3 gems installed
Installing ri documentation for json_pure-1.2.0...
Installing ri documentation for rubyforge-2.0.3...
Installing ri documentation for hoe-2.3.3...
ERROR: While executing gem ... (EBADF)
Bad file descriptor - read(2) failed
Assertion failed: (0), function lock, file vm/util/thread.hpp, line 309.
I haven't been able to reproduce this reliably, if i can get more information out of it, I'll add it to this issue.
This has likely been fixed.