XLL loading fails unless load through File Open
 

I have an XLL that will not load in Excel (fails with error "this file is not
in a recognizable format...") when I drag it in or load it on startup (
c:\start excel.exe myxll.xll ). But when I open it via File Open
myxll.xll , it loads properly. What could the problem be? Or how could I view
verbose debugging output from Excel?