I have a similar problem.
Originally had Win 8 Release Preview (64-bit).
Purchased legitimate copy of Start8, verison 1.0. Ran great.
Win 8 Release Preview today told me that it is expired.
First, I uninstalled Start8 (just in case of Internet registration stuff).
Then re-formatted hard drive and installed Win 8 RTM (64-bit).
Bear in mind that this is a perfectly fresh/clean install of Win 8: I installed Start8 1.0, and it won't run. No start button, no nothing. Rebooted multiple times. Still nothing.
Then uninstalled Start8 (it shows up in Control Panel > Programs). Downloaded Start8 1.10. Installed it. No start button, no nothing. Rebooted multiple times. Still nothing. Checked for files in C:\ProgramData\Stardock\Registrations -- folder is completely empty. Checked certificate signing dates: all say 1/10/2013. Tried going into folder C:\Program Files (x86)\Stardock\Start8 and running the various .EXE files in there. None of them show anything on-screen.
Task Manager > Services says that "Stardock Start8" service is running. Task Manager > Processes shows "Stardock Start8 Configuration Utility (32-bit)" [sic] is eating up ~33% of the CPU. But still nothing appears on-screen.
What should I do now?