I have Safari Beta 4 on my Apple G4 PowerPC Powerbook. I get this message everytime I open WebKit. Present version -Version 4 Public Beta (4528.16, r42114 WebKit failed to open correctly on your previous attempt. Please disable any Safari extensions that you may have installed..... I don't have any Safari extensions, though I do have Safari 4 Modifier which turns off the new features in Safari 4 Beta. But I get the error message even when I go back to the default features of Safari 4.
*** Bug 25719 has been marked as a duplicate of this bug. ***
I also have Safari Beta 4. I have a MacBook Intel Core Duo running Mac OS X 10.4. I get the same error when opening the nightly build of Webkit (Version = 530.11+, r43808). It still opens normally though and seems to work without any problems. I didn't get the error when I opened WebKit for the first time after downloading it last night. I didn't change anything though. Just shut down my Mac for the night.
WebKit Nightly gives the same dialog to me also, since installing Safari 4 beta. If I set aside com.apple.Safari.plist, then WebKit does not give the dialog on the next launch. The dialog returns, however, on the 2nd launch. This with NO input managers and NO plug-ins installed. (I even pulled the system-wide ones in /Library). FWIW, - Dan.
On my PowerBook G4 550Mhz this alert box started when an install of a new build failed to complete and had to be re-installed. I tried on another user and the first launch of WebKit went fine but at subsequent launches the alert appeared. I removed all extensions and anything else I could with no improvement. I have gone back to Safari for the time being. I had a chance to accidentally duplicate the problem on my dual 2Ghz G5. I was installing an update to WebKit and an OSX update at the same time. I had to interrupt the installation and then after re-installing WebKit the alert box appear ed on the next launch of WebKit. I cured the problem by re-installing OSX from a TimeMachine backup. Now WebKit on the G5 launches fine.
As of June 12, I no longer experience the bug. Pershaps one of the nightly updates to Webkit fixed it. Thank you all you Webkit experts.