I mentioned earlier in the chapter that because using Classic involves so many layers, there are more places where things can go wrong. In addition, because Classic boots up a full version of Mac OS 9, most things that could go wrong in OS 9 can also go wrong in Classic. Although I can't spend too much time talking about troubleshooting the Classic Environment, here are some of the most common problems people have with using Classic. In addition to the issues discussed here, Appendix A includes a discussion of some of the problems you may encounter when switching between booting into OS X and OS 9.
As I previously explained, just as OS 9 was sometimes plagued by startup file conflicts, the Classic Environment can suffer the same fate. If you find that Classic is freezing during startup, or that Classic applications are behaving oddly (but OS X applications are working fine), the problem could be caused by startup files that don't play well together.
As under OS 9, the first step towards determining if a startup file is at fault is to start Classic with extensions and other startup files disabled. In the Advanced tab of Classic preferences, under Startup Options, choose Turn Off Extensions from the pop-up menu, and then click the Start Classic button. If Classic loads properly and your problems are gone, a startup file conflict is probably the culprit. (If not, then some more advanced troubleshooting methods are in order.)
How to manually discern which startup file(s) are the source(s) of your problems is both too deep (in terms of length of the discussion) and too basic (this kind of troubleshooting has been around the Mac platform for 15 years or so) a topic to get into here. Instead of explaining the procedure, I again recommend that you download Casady & Greene's Conflict Catcher if you don't already have a copy. Besides its excellent startup file management abilities, which I talked about earlier in the chapter, it also has an automated conflict test feature to help you find the cause of startup file conflicts. Even though Conflict Catcher was written for Mac OS 9, it has been updated to run within the Classic Environment. Best of all, whereas the testing procedure in OS 9 required multiple restarts of your computer, when Conflict Catcher runs in Classic, you can do other things on your computer; Conflict Catcher will automatically restart Classic in the background as it tests.
It's bound to happen sooner or later—one of the applications you're running in Classic crashes. Unfortunately, Classic isn't as stable as Mac OS X, so chances are the application won't exit gracefully. If it crashes and quits, chances are it will cause the entire Classic Environment to crash and quit as well. However, it may be frozen, or it may freeze the entire Classic Environment. If so, here are some ways to get out of it.
If one of your Classic applications freezes, you should generally treat it just like any other application, and use one of the methods discussed on Chapter 7 to force quit it. However, be aware that force quitting a Classic application will almost always force the entire Classic Environment to quit; you should first try to save any changes in open documents in other Classic apps.
In addition to Classic application freezes, sometimes the Classic Environment itself will crash or freeze. If it crashes, it will usually quit entirely (taking any running Classic applications with it). However, if it freezes, you'll need to quit it yourself. The easiest way to escape a frozen Classic Environment is to click the Force Quit button in the Start/Stop pane of Classic System Preferences. This will quit Classic immediately, along with all Classic applications, without giving you a chance to save your work. (Although that's probably not an issue if you've resorted to force quitting Classic.) If this doesn't work, remember that Classic is simply an OS X application; you can use any of the procedures I listed in Chapter 7 when I discussed how to force a misbehaving application to quit.
Sometimes a Mac OS 9 System Folder that you know exists isn't listed in the Classic pane of System Preferences. You can often remedy this by switching to the Startup Disk pane of System Preferences, selecting that System Folder as the startup OS, then switching back to Classic preferences (you may need to quit System Preferences and relaunch it in between). Generally the System Folder will now appear as a valid selection for use in Classic. After you've selected it, be sure to go back to Startup Disk preferences and re-select your normal startup volume as the startup OS.
Another solution, if this one doesn't work, is to open Terminal and type sudo bless -folder9 "/System Folder" -setOF <RETURN> (if the System Folder you're trying to use for Classic is located on the boot volume) or sudo bless -folder9 "/Volumes/volumename/System Folder" - setOF <RETURN> (if the System Folder resides on a different volume; volumename is the name of the volume). This command tells Mac OS X that the referenced System Folder is indeed a bootable (and thus selectable) System Folder; you should then be able to select it in Classic preferences.