How do I remove corporate administrator settings?
Converting my comment into an answer, as it proofed according to its follow-ups:

In a thread at XDA, a user states:


  I had the same problem when i tried to setup an exchange email account and installed a certificate. Fixed it by deleting all certificates. Settings>Security>Clear credintials


So I'd suggest you just do that.

For additional information, also take a look at this thread at Android-Forums, which deals with the same problem you mention as example in your question ("screen pattern lock" -- here: disable lock screen).