You might try reinstalling the toolkit but the installer should have created the following directory:
C:\Program Files\National Instruments\LabVIEW 6.1\vi.lib\addons\internet
Within this folder, there should be a folder for:
ftp
http
image
smtp
telnet
url
utils
and a file dir.mnu
It could be that the toolkit was intalled to the wrong folder. In which case you can move the folders and reboot LabVIEW.