At the university I work at, we have a lab with various Macs including some PPC eMacs and newer Intel iMacs. Anyway, on one of the PPC eMacs, Safari won't open. On the student account, the icon bounces once and stops, on the admin account, it just keeps bouncing. Regardless which account it's on, it never actually opens, or even comes up with the Safari menu bar at the top. When on the student account, it seems to quit itself, but I have to force quit on the admin account to get it to stop "trying" to open.
The machine is a 1.25GHz PPC G4 running 10.4.11. I've tried repairing permissions as well as completely deleting and resinstalling Safari (downloading via my laptop and copying the install package over to the offending eMac through Remote Desktop). I have one other identical machine as this (same specs and OS) and it's working fine on it.
I'm just hoping the next step isn't a complete OS reinstall, as we got these eMacs before I became responsible for this lab, so I have no clue where the original install discs are... :(
It sounds like the machine in question may have gotten installed on it a "helper" like AcidSearch or PithHelmet. Look in /Library/Input Managers or ~/Library/Input Managers and see if any suspicious Safari-related items are in there. Also check /Library/Application Support and see if there is a SIMBL folder and a Plugins folder within that.
I was using AcidSearch, which enabled Safari's search window to use search sites other than Google. At some point the developer stopped keeping up with Safari updates, and after a 3 dot- something update, my Safari app would not launch until I cleared out the Input Manager and SIMBL items.
Worth a shot, anyway.