Messenger Plus! Live does nothing to prevent you from signing in. It too does not touch any settings or options. So, if you can't sign in after installing Messenger Plus!, the chance is small that this is because you installed Messenger Plus!. Something else must be at fault...
Also, make sure you have downloaded Messenger Plus! from the official site:
http://www.msgpluslive.net/ and from nowhere else (there are fakes out there. eg: IMPlus is _not_ Messenger Plus!.).
Anyways, when reporting problems, always give as much as details as possible. Especially error codes.
Here is a link which gives you official solutions for error code 80072EFD:
http://messenger-support.spaces.live.com/blog/cns...8B853F!13953.entry
Read everything very carefully and follow the proper steps. Good luck...
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