In response to Rick's question, maybe there's a doctor on the list that can provide a more definitive answer, but in the meantime WebMD contains the following 2 statements, which are similar to what I've read elsewhere: 

"When an infected tick bites you, bacteria travel to the tick's salivary glands and then into your body through your skin. It takes about 24 hours for a tick to attach itself to the skin and begin to feed. The tick generally must be attached to you for 36 to 48 hours in order for it to transmit the Lyme disease bacteria."

"Experience suggests the tick must be attached for at least 24 hours for the person to become infected. This is not always true 100% of the time, but it's a good rule of thumb."

Not exactly the same, but I don't think inconsistent: my interpretation is that you're unlikely to get infected before 24 hours, you can get infected from 24-36, and you're more likely to get infected after 36.  So it's not really hard to prevent, but you do have to find the dang little thing.

Jason Waanders
NW DC
jwaandersATstarpower.net