Uploading to Uno board

Hi Folks,
Using programs that I have uploaded before, today I found that I cannot upload any program to my Arduino Uno board. I can only assume that it is either the cable or the board itself. Any ideas, or are there any check programs that I can run.
Cheers,
Michael

what error message are you getting?

has it worked before?

if no:

are you on windows 7?

if yes: http://arduino.cc/it/Guide/Windows