I just tested this on VL6 Light Live and soho alpha, both worked correctly. I had a terminal open (xterm and konsole, respectively) logged into root, and ran the menu 'gslapt' option. I was prompted for password, supplied it, and gslapt opened correctly. Both of these tests were on fresh installs so perhaps the issue is related to updates that have taken place since the fresh install. I will check on my laptop (VL6 Standard + updates; kernel too) and report back.
edit: just checked my laptop and it also works fine given the scenario above (open xterm, logged into root, start gslapt, opens normally).