Correction: Enclose 1.0.3 works on Snow Leopard, but not if you've been running Enclose on Leopard (10.5). New users on Snow Leopard should be fine. The real problem is reading the Leopard-created internal Enclose database when running Enclose on Snow Leopard.
Here's a beta version of the next Enclose release should should allow current Enclose users to upgrade without problems. If you are an Enclose user upgrading to Snow Leopard, please try it and let me know your results, positive or negative.
Enclose 1.0.4b2(While downloading, the link opens a blank window--just close it.)