It's quite strange: Arduino 1.5.2 contains the same version as Arduino 1.03!
Why is that strange? Those two releases from from about the same timeframe; one is for Due/etc, and one is the AVR-only version.
This is the first I've heard that the serial monitor mode is broken in the latest version; the bugfix for Issue 392 should only stop !!! from entering the monitor during an actual upload. Sigh.