I’ve installed some programs that place useful icons in my menubar. But after I restart the computer, a bunch of these icons disappear. I even upgraded to Snow Leopard, and the same problems remain.
You’ve stumbled upon a long-standing bug that dates back to the days of Mac OS 10.5 and is still troublesome in Snow Leopard. It isn’t a problem with your menubar icons per se, but rather a problem with the login items mysteriously disappearing from System Preferences > Accounts. Judging by the number of complaints about this issue on Apple’s Discussion Forums, we assure you that you’re not alone in your frustration. The bad news is that there’s no current solution to this problem, though we do have some useful options for you. But to start, we recommend submitting your bug report to Apple’s Mac OS X feedback page (www.apple.com/feedback/macosx.html). In the meantime, a few workarounds can help. Your login items are controlled by the loginwindow.plist file located in your ~/Library/Preferences folder (that ~/ means it’s inside your home folder, by the way). So after you’ve set all of your login items the way you like ’em, make a backup copy of this file. The next time your login items misbehave and remove themselves, restore your backed-up file to its original location, log out of your Mac and log back in, and hopefully the login items will stay put.
Keep an eye on System Preferences > Accounts for mysteriously vanishing login items.
Another useful tactic is to lock the loginwindow.plist file in the Finder. Click once on the file, choose File > Get Info, and select Locked. This will prevent your login items from removing themselves, but it will also prevent new login items from being added. So remember to unlock this file before making any changes to your login items, and then lock it again afterward.
Locking the loginwindow.plist file in the Finder will prevent any changes, unintended or not.