I ran the two commands you suggested. However, the second one told me that "LOG BACKUP" was needed. So, I performed another log backup and then did a SHRINKFILE on the log and Voila!

I now have a 4Gb log file once more! 🙂

What puzzles me though is the fact that after doing my first log backup that this didn't solve the problem. It seems doing the second one was needed, but I don't know why.