Signature error with create folder

I keep getting this error when trying to create a new folder via the ruby lib.

```
1.9.3-p125 :006 > folders.create('Foo')
ContextIO::API::Error: Invalid signature
	from /Users/sharad/.rvm/gems/ruby-1.9.3-p125/gems/contextio-1.2.3/lib/contextio/api.rb:103:in `request'
	from /Users/sharad/.rvm/gems/ruby-1.9.3-p125/gems/contextio-1.2.3/lib/contextio/folder_collection.rb:14:in `create'
	from (irb):6
```

I can access other folders, get their names, etc. just fine, but create fails. Here is what the response body received looks like (from lib/contextio/api.rb):
```
"{\"type\":\"error\",\"code\":105,\"value\":\"Invalid signature\"}"
```

I am not sure why the signature would fail for create, when it works just fine for other calls.

Thanks for your help.

-Sharad