Thanks all. Shortly after posting this on the forums, I realized the problem was indeed a loose shifting cable, and got that fixed immediately. However, while the derailleur moved to the top ring, the chain was rubbing quite fiercely against the derailleur cage. Turns out the 105 brifters have a trim-relief that allows the derailleur to be moved over slightly farther, thus relieving the chain rub, though the reasons why are still a little foggy for me. Either way, it was working great until I kept having an issue with not getting the derailleur dialed in where I need it. I realized part of my problem was that the threads for the high-gear limiting screw were stripped out on the actual derailleur body...soooo now I'm in the market for a new front derailleur.

I'm thinking of just picking up a cheap Sora 2x9 front derailleur for practically just shipping costs on eBay, though the new Shimano FD-CX70 looks quite appealing. Considering I decided to upgrade my Tektro Oryx's to a complete set of Avid Shorty 4's I also found on eBay for a good price, I'll probably just try out the Sora and go from there.

Thanks for your replies!