Colloquy has an annoying issue if the Safari 3 beta is installed: if you scroll back in the message history to catch up on something, as soon as a new message arrives you'll end up at the very top of the history.

The obvious solution is to get rid of Safari 3. I only really installed it to try the fancy search-in-page. The disk image contains an uninstaller. You'll be prompted to restart your computer after uninstalling.