having a problem with the gas can....

[Sexbad]

I assume you mean the gas can for fueling the giant earth-eating metal monster in Overture? If I'm mistaken, tell me.

I don't see any logical reason why you can't pick it up, so it's probably a bug. Bugs like these are normally able to be squashed by loading the latest save spot from before you entered the level that contains the gas can.