I dont consider myself part of the brains trust but I hope this is some help to you:
Your problem could be any number of things from fuel pump/filter, sidestand switch or simply the battery is on the way out. Do you have it serviced regularly? When were the valve cleareances last checked?
It is most likely an electrical or fuel problem; what I did on mine once when I had a simaler problem was whip out the fuel injector turn on the key and see if theres any gas squirting out. there was so next I checked the spark, there wasn't any. from there it was a matter of checking and eliminating possible causes...turned out the coil lead had come loose. Easy fix chopped 10mm off the end of it and refitted.
I don't know how mechanical you are but my standard check list for this type of problem is the basic FACTS rule of thumb, namely check the following:
If you can determine which of these is not your problem then that should at least point you in the right direction.... and give us some more clues
Hope this helps