Fooling around in the System folder with invisible files showing !!
Gotta be careful in there - heh, but you know that now, I guess.
Try zapping the pram - hold Command, option, P +R keys at boot. Hold them down til you hear three bongs/chimes.
Try resetting the SMC - go here to find out the correct way for your machine http://support.apple.com/kb/ht3964
I'd grab a copy of disk warrior http://www.alsoft.com/diskwarrior/index.html and try and boot from that - It should...