Well, since no-one else answered this...
Did you solve this yet? If not, did you know about the -sc some_folder switch on the command line that invokes slickedit - you can use it to specify a different configuration directory. Look up "invoking" in the help. Maybe something's gone wrong with the permissions in the config folder you're using. If slick succeds in creating a vslick.stu file in a different folder, you could copy over all the files from your current config folder into the new one (except for any vslick.stu file). With vunxdefs.e, you'll need to explicitly load it - type the name (including full path) on the slick command line and press return. You can use the environment variable VSLICKCONFIG to switch the config folder too. If you end up using a non default config directory, you need to take care when installing an upgrade.
Apart from vslick.stu, does slick succeed in writing any files to your config folder e.g. vrestore.slk or something.
Graeme