FOXSTRONG  Go to yourname/library/application support/SIMBL/plugins/

then delete it.  
(Version 2.8.4)

MISHA  Version 2.8.4, released June 8, fixes this.  
(Version 2.8.4)

PNN314  No, Videobox 2.8.4 has the same problem: Safari 4 won't startup because of VideoBox!!!

Uninstalling and reistalling Videobox does not solve the problem!!!

Videobox needs to be updated.  
(Version 2.8.4)

MISHA  Try 2.8.4 again... they rev'd the build (but kept the version #) and say it should work. If it still doesn't, contact the devs.  
(Version 2.8.4)

WLESTER67  I followed Foxstrong's advice and it worked. Now I can finally start Safari.

At MacRumors:Forum, the developer says to download the Videobox 2.8.4, and he says that it is free. The website wants $15.00.  
(Version 2.8.4.1)

MISHA  The update is free. The app itself costs $15 if you don't already have a copy.  
(Version 2.8.4.1)

COLLIN BLACKMAN  Same deal downloaded and installed Safari 4 - would not load up so used App Cleaner to remove videobox then ran script to remove plugin. Success all go now, will re install VideoBox later. http://download.tastyapps.com/TastyAppsAVPluginUninstaller.zip  
(Version 2.8.5)