Uploading problem, Mega2560 R2

Hi

I am new to arduino, and someone loan me an arduino mega2560, I have trouble uploading code sometime, it usually work fine a few time and then the uploading process take forever, and eventually time out.

And I will have to reboot my computer, or reset the ISP Clock through AVR Studio, every time the error happen, I found the ISP Clock in AS5.1/6 set to 7kHz or 8kHz, and I will need to reset it some figure greater than 13kHz.

What could be the problem and how to I fix it.

It ok but I really don't want to reboot my computer every half an hour, it takes a while for my machine to reboot :0