[Plugin: Constant Contact for WordPress] Error Authenticating – No Error Message

When trying to configure the plugin after installing, I get a red bar (where the error should be) but it’s blank. I have double checked my username and password. It appears that Constant Contact is returning an empty result? Any help would be much appreciated. Here is a var_dump of the cc object:

[Dump moderated as per the Forum Rules. Please use the pastebin]

http://ww.wp.xz.cn/extend/plugins/constant-contact-api/