I second the suggestion to go through the entire front derailleur adjustment, step by step without skipping any. Here's a good one: http://www.parktool.com/blog/repair-...ur-adjustments Do not open up the high limit adjustment any farther than needed to shift reliably; any farther will risk dropping the chain.

It is also possible that your technique could use some fine-tuning. When shifting to a larger ring ease off tension on the chain but keep pedaling at the same cadence. Any tension on the chain will fight against it moving up onto the larger ring. Assuming indexed shifting. it might also help to hold the shift lever over momentarily until the chain shifts and then release it rather than just "clicking" it into position and waiting for the chain to shift.