Symptom
After pressing the Command-Power key combination, or the programmer's button, the Microbug debugger box does not appear in the Classic environment as it would if the computer had been started up from Mac OS 9. The programmer's button is also known as the debugger button or interrupt button.
For further information on Microbug, see article 30556: "
Mac OS: Empty White Box on Screen"
Solution
Mac OS X does not work with the ROM-based debugger in Classic. To use Microbug, start up the computer in Mac OS 9. To debug Mac OS 9 programs in Classic, use MacsBug or another Classic-compatible third-party debugger. Developers can download MacsBug at:
Apple Developer Connection
http://developer.apple.com/tools/debuggers/
MacsBug is a developer tool. As such, technical support for MacsBug is not provided as a part of Apple's normal consumer product support.
Note: Even when using a Classic-compatible debugger, the programmer's button does not work in the Classic environment. To open a debugger in the Classic environment, use the appropriate keyboard command, which is Command-Power on those keyboards that have a Power button, and Command-Eject on those that do not. On some portable machines, you may have to hold down the Command-Eject combination for a moment until the debugger window appears.