After pulling off one the all-time great comebacks, Apple has issued an unexpected profit warning. The problem is due - the company says - to a shortage of G4 processors from Motorola. The G4 is the super-chip that will power Apple's next generation of PowerMacs and iMacs. In fact the company is claiming to have taken 150,000 advanced orders for G4-based machine already. Motorola manufactures the chips for Apple and this delay in shipping the G4 will hurt the Mac makers sales. According to news wire reports, Motorola said the demand for the G4 Macs had taken everyone by surprise. It said it would up production of G4 chips in a short period of time, but didn't specify how short this period was likely to be. Some customers are inevitably going to be left waiting to take delivery of their G4 Macs but, again, no indication was given as to how lengthy such delays might be. ®