[chef] ohai 6.18 and 6.20 failing on ec2 hi1.xlarge

hai.

I don't know if the instance type has anything to do with this, but ohai is
failing on the only ones we use of this ec2 instance type. Ohai and chef had
been running fine on these for many weeks, but today started failing, and
I don't know why. Nothing changed that I know of.

In general, we run chef 11.6.0 (ohai 6.18.0), but I grabbed 11.8.2 / 6.20.0 to
see if the behavior would change, and it didn't.

On the problem host, accessing user-data and meta-data work just fine using
"curl http://169.254.169.254/latest/user-data", etc.

But "ohai -l debug ec2" throws:
 #<RuntimeError: Encountered error retrieving EC2 metadata (returned 404 
response)


[2013-12-12T20:36:14+00:00] DEBUG: Loading plugin ec2
[2013-12-12T20:36:14+00:00] DEBUG: has_ec2_mac? == true
[2013-12-12T20:36:14+00:00] DEBUG: can_metadata_connect? == true
[2013-12-12T20:36:14+00:00] DEBUG: looks_like_ec2? == true
[2013-12-12T20:36:14+00:00] DEBUG: EC2 metadata version: 2012-01-12
[2013-12-12T20:36:14+00:00] DEBUG: Plugin ec2 threw exception #<RuntimeError: 
Encountered error retrieving EC2 metadata (returned 404 response)> 
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/ohai-6.18.0/lib/ohai/mixin/ec2_metadata.rb:104:in
 `metadata_get'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/ohai-6.18.0/lib/ohai/mixin/ec2_metadata.rb:120:in
 `block in fetch_metadata'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/ohai-6.18.0/lib/ohai/mixin/ec2_metadata.rb:113:in
 `each'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/ohai-6.18.0/lib/ohai/mixin/ec2_metadata.rb:113:in
 `fetch_metadata'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/ohai-6.18.0/lib/ohai/mixin/ec2_metadata.rb:130:in
 `block in fetch_metadata'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/ohai-6.18.0/lib/ohai/mixin/ec2_metadata.rb:113:in
 `each'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/ohai-6.18.0/lib/ohai/mixin/ec2_metadata.rb:113:in
 `fetch_metadata'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/ohai-6.18.0/lib/ohai/plugins/ec2.rb:52:in
 `from_file'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/ohai-6.18.0/lib/ohai/mixin/from_file.rb:29:in
 `instance_eval'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/ohai-6.18.0/lib/ohai/mixin/from_file.rb:29:in
 `from_file'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/ohai-6.18.0/lib/ohai/system.rb:216:in
 `block in require_plugin'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/ohai-6.18.0/lib/ohai/system.rb:211:in
 `each'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/ohai-6.18.0/lib/ohai/system.rb:211:in
 `require_plugin'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/ohai-6.18.0/lib/ohai/plugins/cloud.rb:19:in
 `from_file'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/ohai-6.18.0/lib/ohai/mixin/from_file.rb:29:in
 `instance_eval'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/ohai-6.18.0/lib/ohai/mixin/from_file.rb:29:in
 `from_file'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/ohai-6.18.0/lib/ohai/system.rb:216:in
 `block in require_plugin'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/ohai-6.18.0/lib/ohai/system.rb:211:in
 `each'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/ohai-6.18.0/lib/ohai/system.rb:211:in
 `require_plugin'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/ohai-6.18.0/lib/ohai/system.rb:140:in
 `block (2 levels) in all_plugins'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/ohai-6.18.0/lib/ohai/system.rb:133:in
 `each'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/ohai-6.18.0/lib/ohai/system.rb:133:in
 `block in all_plugins'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/ohai-6.18.0/lib/ohai/system.rb:131:in
 `each'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/ohai-6.18.0/lib/ohai/system.rb:131:in
 `all_plugins'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/ohai-6.18.0/lib/ohai/application.rb:97:in
 `run_application'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/ohai-6.18.0/lib/ohai/application.rb:75:in
 `run'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/ohai-6.18.0/bin/ohai:51:in `<top 
(required)>'
/opt/chef/bin/ohai:23:in `load'
/opt/chef/bin/ohai:23:in `<main>'


Is this known? Any help or work arounds?

thanks!
kallen