Thanks for the guys who attempted to solve my problem. As suggested in the FAQ, I did give permissions to ASPNET user for my log directory. The mistake that I did was that my ASPNET user was trying to fetch the ProcessName (which needs Unrestricted Security) before it even adds the Appenders to the logger. So, when this fails, log4net gives up adding any Appenders. Hence, no log file.
Lesson learned: Don't assume that the thirdparty component is always at fault. Your component might have been the culprit too. Again, a big thanks to all those who are doing a fine, fine job helping all us developers waddling through the mire. Sridhar