The block heater should not have anything to do with the transmission lines as far as I know, but my truck is a 2005. I did have a coolant leak at the torqueconverter cooler (looks like a small radiator mounted near the firewall near the front of the transmission.) The coolant looks almost like trans fluid so make sure the leak is not coolant.
I did a quick search on Turbo Diesel registry web suite and did not see anything specific on the trans lines leaking, but several posts on the coolant leak going to the cooler? You might also try posting here:
http://www.cumminsforum.com/forum/index.php