maybe you´re using firefox or some other browser than internet-explorer?
On my machines, the Remote-Acess or Computers tab (sorry, don´t know the exact name now) isn´t displayed, too if using Firefox.
Or did you maybe change the corresponding attribute for the user in the WHS console (under User->Properties->Remote Access - There´s a dropdown menu where you can select that the user should see both tabs in the webinterface or just remote access or just shared folders)?