Christian is right - use the high speed comms option. Set it for 12 clock. Choose a baudrate that works from the drop down box.

What then happens is that the device measures the slower initial baudrate. Once the device and Flash Magic can communicate, Flash Magic reprograms the timer generating the 66x's baudrate, allowing for faster baudrates as the error is minimized.

On recent versions of Flash Magic this higher baudrate is shown at the top of the Flash Magic window while you are performing ISP operations. This allows you to see what speed they are really communicating at.
Note that unlike an 8051, PC COM ports are limited to specific baudrates. Therefore the higher baudrate used can only be one supported by the PC.

Andy
Embedded Systems Academy