I just ran across this, ironic since I just updated a test computer from CTP5 to CTP6and wondered why it wasn't working;
"We have recently discovered an issue with SQL Server 2008 CTPs that result in SQL Server 2008 not starting or installing on Feb 29 GMT only. We recommend that you do not run, install or upgrade this CTP on Feb 29 GMT to minimize any impact in your environment. You can install starting on March 1 GMT. If you have an immediate issue that cannot wait until March 1st GMT contact email@example.com before taking any further steps."
I mean, I know it's pre-release and all but come on - leap year?