It could also be a matter of cable tension or FD limit setting. Try Brad's recommendation first and then go through the process of adjusting the limit and cable tension if the lubricant did not help. Any or all of those conditions may be contributing to the problem.

Can you make the FD shift to the big chainring by pulling on the cable by hand? Does the shift lever actually click into the third index when you try to shift to the big chainring? Is there a lot of slack in the shift cable when you have the chain on the smallest chainring?