Since version 4.84, Messenger Plus! is created with Visual Studio 2010, in preparation for the development of Plus! 5. However, a minority of users could not use this Windows Live Messenger extension anymore properly due to the changed DLL format.
This is why a minor update for Plus! 4.84 has been released. It addresses the DLL problem. The change log states:
The move to Visual Studio 2010 caused Messenger Plus! to stop working for a minority of users. The resource DLL of Messenger Plus! has been modified to solve this issue.
You can go ahead and download the update right now.
Note: Do not try to use this version of Messenger Plus! with any version of Windows Live Messenger 2011 (Wave 4). It will not work.
Download: [download id="4"]