GitHub User: jdresner
I had this issue. I develop on Windows 7, and certain gems have windows-specific versions. I went into my Gemfile.lock and removed all "x86-mingw32" in the gem version numbers. After commiting the changes and deploying again, it worked.
I also had this problem with postgres and the pg gem.
Answered my own question. Rewrote the unicorn_init.sh file on a Unix machine instead of my usual Windows box.
Did you ever find an answer to this? I'm can't seem to beat this one.