Hello All, I am newbie to MAC. I am writing a Device Firmware Updater for a Bluetooth Headset device on Mac OS X 10.5.7. while downloading the firmware I keep on getting "Transaction Timeout" errors very frequently. The application runs successfully for firmwares having size less than 700KB but it gives error "Transaction Timeout" for firmware having size 1.2MB. I am writing firmawre on device in block of 1023bytes. My program is writing some blocks and after sometime it halts giving error "Transaction Timeout" Everytime, number of blocks written successfully differs. I am using XCODE, Objective C & COCOA framwork for this. I am using funtion DeviceRequestTO() and structure IOUSBDevRequest for the purpose of writing firmware on device. Please, can anyone help me.....? Thanks in advance.