[chef] Unable to upload cookbook

[Stephen Nelson-Smith < >]

I'm getting the following on attempts to upload my application cookbook:

master ✗ % knife cookbook upload application
INFO: Saving application
INFO: Validating ruby files
INFO: Validating templates
INFO: Syntax OK
INFO: Generating Metadata
INFO: Uploading files
INFO: Uploading  (checksum hex = ) to 
https://s3.amazonaws.com/opscode-platform-production-data/organization-37c9c504005c48fb95db81d246f263ed/sandbox-cc49c00dbe0840fa81e65ae479a4d53f/checksum-?AWSAccessKeyId=AKIAJOZTD2N26S7W6APA&Expires=1294587770&Signature=p8cPSpgrAWIM0PihaJzNONrmFMI%3D
/Users/stephen/.rvm/gems/ree-1.8.7-2010.02/gems/chef-0.9.12/lib/chef/cookbook_uploader.rb:39:in
 `read': can't convert nil into String (TypeError)
        from 
/Users/stephen/.rvm/gems/ree-1.8.7-2010.02/gems/chef-0.9.12/lib/chef/cookbook_uploader.rb:39:in
 `upload_cookbook'
        from 
/Users/stephen/.rvm/gems/ree-1.8.7-2010.02/gems/chef-0.9.12/lib/chef/cookbook_uploader.rb:30:in
 `each'
        from 
/Users/stephen/.rvm/gems/ree-1.8.7-2010.02/gems/chef-0.9.12/lib/chef/cookbook_uploader.rb:30:in
 `upload_cookbook'
        from 
/Users/stephen/.rvm/gems/ree-1.8.7-2010.02/gems/chef-0.9.12/lib/chef/knife/cookbook_upload.rb:67:in
 `run'
        from 
/Users/stephen/.rvm/gems/ree-1.8.7-2010.02/gems/chef-0.9.12/lib/chef/knife/cookbook_upload.rb:65:in
 `each'
        from 
/Users/stephen/.rvm/gems/ree-1.8.7-2010.02/gems/chef-0.9.12/lib/chef/knife/cookbook_upload.rb:65:in
 `run'
        from 
/Users/stephen/.rvm/gems/ree-1.8.7-2010.02/gems/chef-0.9.12/lib/chef/knife/cookbook_upload.rb:80:in
 `humanize_auth_exceptions'
        from 
/Users/stephen/.rvm/gems/ree-1.8.7-2010.02/gems/chef-0.9.12/lib/chef/knife/cookbook_upload.rb:53:in
 `run'
        from 
/Users/stephen/.rvm/gems/ree-1.8.7-2010.02/gems/chef-0.9.12/lib/chef/knife.rb:127:in
 `run'
        from 
/Users/stephen/.rvm/gems/ree-1.8.7-2010.02/gems/chef-0.9.12/lib/chef/application/knife.rb:121:in
 `run'
        from 
/Users/stephen/.rvm/gems/ree-1.8.7-2010.02/gems/chef-0.9.12/bin/knife:25
        from /Users/stephen/.rvm/gems/ree-1.8.7-2010.02/bin/knife:19:in `load'
        from /Users/stephen/.rvm/gems/ree-1.8.7-2010.02/bin/knife:19

I'm not sure what I've changed - every other cookbook seems to upload ok, but 
this doesn't....

The src is:

file_contents = File.read(checksum_files[checksum])

Which suggests some checksum oddness...

Any ideas?

S.