Plain old shift key is safe mode. Boots with much fewer drivers and no startup items.
command-S is to do a file system directory cleanup via command line /sbin/fsck -fy
Option key gives you the option to go to the Lion Recovery partition, and run Disk Utility to do the same thing as /sbin/fsck -fy in Repair Disk or reinstall Lion, which I would not do unless you have troubleshooted all other possibilities of you are having problems. Either way, a backup is important to do before anything else. See my tip:
Do not under any circumstance run a System cache cleaner, or MacKeeper. These are much more pain to remove their side effects than they are worth.
Thanks very much. U backup regularly with time machine to an external drive and I use Dropbox and iCloud! I'm covered, but shift isn't doing it for me. The maintenance protocol I'm following is from cnet and the penultimate step is to repair permissions using disk utility run in safe mode, but I can't get there. Would u recommend I try the other approach u mention? It's odd. Thanks again.
Repairing permissions in safe mode is not absolutely necessary. It works just as well when booted in regular mode. But it does help to remove any startup items from your user's preferences in the System Preferences and reboot and quit all open applications. Repair Disk is neither safe mode, nor done in regular boot. That's done when booted with command-S, or booted off the recovery partition in Lion, or Mountain Lion. If your Mac is running 10.6.8 or earlier, boot off the 10.6 installer disk and use the Disk Utility there, usually in the Utilities menu.