[crb07]

If you purchased your bike recently or use a regular shop take your bike there in your shorts and shoes that you ride in. Get properly fitted and a saddle that they recommend if yours is not comfortable. (if your shop is crap and they are not professional you are waisting your time). If your bike does not fit you or is not set up properly you may be doing more damage to your body than good. If you still have chafe try any of the products your local shop sells for this.
If you are sure your bike is set up correctly then I would say it is your shorts or saddle. I can due 3-4 hour rides 4-5 times a week and have no problems in htis area.