First, a drop can be more than enough to cause a problem. Second, it is a LIQUID; it will FLOW. Thus, you may not see anyting for a while as the liquid spreads and moves around with the motion of the device. And third, it can take a while to dry, and putting the battery back in while there is still moisture inside can ruin it, if it was not already damaged beyond repair before you removed the battery.
From your description, moisture exposure appears to be the most likely possibility as the cause of your problem. You can look at other possibilities after you have made sure the device is dry, but you must dry it first. Though it may be too late now, see Got Your BlackBerry Wet? - BlackBerryFAQ
If after you have made sure it is dry and you still have trouble, you could try wiping and reinstalling the OS. There may be possibilities that involve software conflicts that could be dealt with less drastically, but I don't know what they are, or if there are any.
So, see the FAQ article on drying out the blackberry. Do that and then see what you got. Post an update after.