What kind of handlebars do you have on the bike in question, and are they different than what you're used to? The reason I ask is that the couple of times I've gotten on a road bike with drop bars, it has been a major swerve-fest that I haven't had the guts to take out of the parking lot because I felt like I was about to crash the whole time. I'm used to flat bars, which seem to be much more stable especially if you're a bit of a twitchy rider anyway, and I couldn't even get a comfortable hand position on the narrow drop bars. It would take some major getting used to for me to ride with that type of setup, and it's probably the same for anyone changing to a totally different configuration. If you're doing so, that may be part of your issue and will improve with practice.