[mde3]

Maybe just fresh gas...water is heavier than fuel so it will be at the bottom of the tank after sitting for so long...Maybe condensation and maybe bad bad gas too..try some new fuel for starters. Always look for the simplest solution first. In todays high cost fuel market, it is not unheard of for some stations to end up with "watered gas" from buying fuel on the "spot market" (when you see an unmarked tanker unloading fuel at your local BP or Sunoco..be wary)..so if at some point you ended up with some water in your tank...all of it would now be sitting at the bottom and maybe even above the pick-up point, and could be causing the problem.

Have had this happen a few years ago...the only way to really clear it from the tank is with a weighted syphon to get the pick-up down to the bottom of the tank...you will see the difference in the color of the gas you pull out if this is the problem.

One other possibility as well..a gas cap with a stuck breather..this will create negative prssure in the tank, and can cause fuel starvation after a while...although it sounds like lack of fuel is not the problem.