Put interrupt on my board, now I can't upload!

Using an XBee FTDI to Upload to an Arduino Fio. I had no problems until I uploaded the following code on to the board:

Timer1.initialize();
Timer1.attachInterrupt(changeState,4000000);

(the time period above may have been more frequent than I have posted)
Now whenever I try to upload anything to the board, I get the following error:

avrdude: stk500_recv(): programmer is not responding

While trying to upload a sketch I will see the XBee's RSSI led turn green then I get the above error.

I've tried:

-pressing the reset button then upload at different time intervals
-Disconnecting the USB cable
-Disconnecting all my wires to arduino pins
-uploading latest version of FTDI driver

I am using a mac version 10.7.5.

Help!