BaseCamp 2.1.2 was posted here to fix several issues. It is basically the 2.1.1 Beta version with some additional fixes. Note that this version is mostly intended for PowerPC and Tiger users that can't upgrade to BaseCamp 3.0.1.
It appears there is an issue with the autoupdate feature for user's running 10.5 on a PowerPC Mac. If you are already running BaseCamp 2.1.2 on a PowerPC Mac with 10.5, you may want to turn Check for Updates off in your preferences and not accept an update if you are prompted. Though we haven't had any reports of the issue, it is possible that it will download and install BaseCamp 3.0.2, though it is for Intel Macs only. Sorry for the inconvenience.