Before riding it you should really check that there is no movement in the headset bearings. With the front brake hard on, move the bike back and forwards and feel for movement. By releasing the stem locking bolts for more height, and taking off the pressure on the headset by removing the weight of the front wheel, the h/s bearings may need re-adjusting.
+1 to that. If you did it with the bike on its side, there's a chance that the bearings have dislodged or that you aren't clamped down hard enough.
I think that the best way to check for loose head bearings is to hold the join between the frame and the forks whilst holding the front brake and rocking the bike, you can easily feel movement which you might not be able to see there.
Another quick check is to hold the front wheel off the ground and move the steering through it's full movement to ensure it is smooth and accurate.