There have been some reports of problems encountered when LonMaker is installed in locations other then the default directory. These problems can include failure of LonMaker .dll files to register as well as plug-in registration failure.
LonMaker is not installed in default directory. Typically this refers to the C:\ drive, but it doesn't necessarily have to.
Restrict the LonMaker installation to the default directory and the default LonWorks folder.