I just installed the latest release of the beta for the next release of Lion: 10.7.5. When I went to launch Mail, I was informed that Spam Sieve was disabled because it was incompatible with version 5.3 of Mail. I am running the latest version of SS.
I tried downloading and reinstalling SS but received the same error.
Let me know if this can be solved or I have to report it to Apple as a bug.