[msftguy]

It was 4.2b, my bad. Cydia was using some UI class from a private framework that got removed in 4.2 betas.

[Xuzz]

Yeah, there was _UISwitchSlider class or something being used. I ripped almost all of that stuff out for "Cydia 1.1"; except for saurik's WebKit code to replace the crippled UIWebView, it's almost entirely public APIs now (UIViewController, UISwitch, etc).