Fastcgi crash “asked to stop immediately”

I'm trying to upload files in a rails app with the paperclip gem on
shared hosting with bluehost. It works fine locally, but on bluehost
whenever I try to upload the file I just get redirected to the index,
and a new log file pops up called fastcgi.crash.log in my log
directory. It says:

[18/Nov/2009:09:12:19 :: 23593] asked to stop immediately
[18/Nov/2009:09:12:19 :: 23593] stopping after explicit exit
[18/Nov/2009:09:12:23 :: 3679] starting
My raw access file looks like: - - [18/Nov/2009:09:12:32 -0700] "POST /images HTTP/1.1"
301 421 "" "user agent
Why it's giving a 301 permanently moved redirect is strange ...

I have another app with paperclip that works on a different account
(but still bluehost).

The only difference I can see is that my environment file has this
line in the working version:

RAILS_GEM_VERSION = '2.3.3' unless defined? RAILS_GEM_VERSION

and in the busted one:

RAILS_GEM_VERSION = '2.3.4' unless defined? RAILS_GEM_VERSION

If I switch the busted one to 2.3.3 I get an ugly "Application error
Application failed to start properly" instead of the usual red box.

Any ideas?

-Ryan Florence