Arduino UNO with GPS Shield iteadstudio (avrdude: stk500_getsync(): not in sync)

Hi,

I had just bought this GPS Shield by iteadstudio.
Never had trouble uploading sketch on my Arduino UNO.

So I stacked the GPS shield on the UNO and started to upload a sketch. I was greeted with this error:
avrdude: stk500_getsync(): not in sync: resp=0x2a

somtimes,
avrdude: stk500_getsync(): not in sync: resp=0x54

Anyone knows how to fix this? Is there something wrong with the shield or anything that I can do?
Or is this shield incompatible with Arduino UNO R3?

Thanks in advance. I had tried almost everything the internet has posted but to no avail.

If the GPS is using the same two Serial I/O pins that the USB interface uses there will be a conflict. Sometimes the GPS Shield has some optional jumpers to move the serial I/O to data pins (for use with SoftwareSerial). If not you will probably have to unplug the shield when uploading.

Ya. I have to unplug and do the uploading. XD