Problem uploading sketches

I am having troubles uploading to my official Arduino Diecimila and RBBB boards from Modern Devices. I have tried uploading sketches using versions 11, 12, and 13 of the Arduino software from both Ubuntu Linux and Windows Vista on one computer and Ubuntu Linux on a second computer. Sometimes it will upload once per board after the computer is restarted but subsequent times I get the following errors:

avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_recv(): programmer is not responding

and sometimes:

avrdude: stk500_getsync(): not in sync: resp=0x37
avrdude: stk500_disable(): protocol error, expect=0x14, resp=0x37

(The specific values change each time)

Recently I had problems getting the software to run on my computer but solved the problem by reinstalling gcj as recommended. Before this I had no problems using these same boards and software. Can anybody recommend a solution to this problem?