Lower back sore after bike segment???

Hello everyone!

So I completed my first triathlon race this year yesterday and I totally enjoyed it!  My swim has definitely improved, tested new tri bike, and tested new racing shoes as well.  However, soon after entering T2 and parking my bike, I felt a little pain/soreness in my lower back.  It was dull.  I tried to stretch to make it go away but it didn't so I continued onto the run segment.  It did not go away until after about 3/4s mile.  I did not feel any of this during the bike.  I was in aero for longer periods that I'm used to but I still got up into the pursuit bars every now and then.  I was no longer in aero position the last 3-4 miles due to really bumpy and curvy bike paths.  What do you guys think brought this on?  Could it be due to racing in a tri bike vs a roadie?  I never felt this before in any of my races.  Please help...  >.<

Here's my race report:

http://www.beginnertriathlete.com/discussion/forums/thread-view.asp?tid=432796