I had this problem where sometimes, I would open the console window for the first time since starting UT, and it would be blank. After opening it, it would then start logging the messages.

Typical scenario would be - I start UT with bat file, play for awhile, someone says something which I miss, I bring up console to see what they said... Doh!  It's blank.

The cause turned out to be when I started UT using a .bat file. I don't know the solution, just the cause. I now know to remember to immediately open the console window after starting it with the .bat file, so that I don't miss any message if need be.

Just FYI.