Mac OS 7.6.1 is a maintenance release for Mac OS 7.6 users. This release corrects a variety of problems that have emerged since the initial release of Mac OS 7.6 in January. Included in this update is the CFM-68K Runtime Enabler for 68030- and 68040-based Macintosh computers. Type 11 errors have also been eliminated on PowerPC machines, as they now report the proper error message instead of the generic Type 11 error. Finally, PowerBook users will benefit from a wide variety of bug fixes and compatibility updates for PC cards and serial port use. If you are using any of the following computers you should not install this update: Macintosh Performa 4400 or a Power Macintosh 4400, 5500, 6500, 7300, 8600, or 9600 series computer. PowerBook 3400 users should click on the related link below to obtain the Mac OS 7.6.1 for PowerBook 3400s.