boxhead,
We do not have a compatiable release of MyEclipse available for Eclipse 3.1 RC1, our last release for Eclipse 3.1 M7. If you absolutely must use RC1 then you can download the Manual Install of MyEclipse 3.8.4 Beta for M7 from our “Eclipse 3.1.x” download area, and install it. This is an unstable solution and you *will* encouter bugs, but for the most part it should work (some users have said so). If you can wait we will be releasing Milestone 2 of our 4.0 release soon that will officially be compatible with Eclipse 3.1RC1. I would suggest that you either wait, or use stable builds of Eclipse/MyEclipse.