It could be the brakes or a symptom highlighted when the front brake is used. While I am not familar with the Buell, I would do the following:
1. Support the bike with the front wheel off the ground. Have someome steady the bike and apply the front brake. With the brake locked, grab the front wheel at the 3 and 9 o'clock postions and try to move twist the wheel from side to side. If there is any noticeable play, the front wheel bearings may be an issue.
2. Repeat Step 1 but instead of holding the wheel, hold the sliders and try to move them backward-and-forward. If any movement is felt, the steering bearings require service.
3. Put a dial indicator on the front disc and measure runout. I'm not sure what the maximum runout is, but you should be able to find it on a Buell web site. If possible, do this check with the front wheel mounted on some type of stand. Otherwise, turn the wheel to full lock and tie it in place with a tie-down to prevent any movement. You want the bike rock steady so the measurement is accurate.
4. Check axle, caliper and brake disc tightness.
Good luck.