First, make sure that objects are visible (but if forms toolbar objects are
showing, then this ain't it!).
Tools|options|view tab|objects category|Check "show all"
My next guess is to clean up the windows temp folder.
windows start button|run
and hit enter
clean this up
My next guess is that it's a windows memory problem. If you restart the pc and
open a brand new workbook and start adding controls, do they show up?