ADIR( FileArray, 'I:\WEBROOT\*.*', 'DH') was not able to see the directory either.

The other thing I found interesting is if I try the command:
SET DEFAULT TO I:\WEBROOT\MYSITE\
I get an invalid path or filename error. I can set the default directory to a sub-directory under that directory.

Example: SET DEFAULT TO I:\WEBROOT\MYSITE\IMAGES will work