GTK+ is required to install this package. To install GTK+, try the following line in R:
install.packages('RGtk2')
If any error occurs, then run the above line again. If GTK+ can still not be installed, visit http://www.gtk.org/download/ and install GTK+ 2.x. (For Mac OS users, visit http://r.research.att.com/ to get the recent GTK+ 2.x framework binary.) Then run the above R code again.
After installing the RGtk2 package, run
install.packages('MissingDataGUI')