I need some help getting J2ME and Eclipse 3.1.1 to work together.

I was starting to get serious about J2ME about 15 months ago and, for a
couple of months, put some serious effort into writing J2ME code in Eclipse
3.0.1. Then, I got sidetracked into some other projects and had to put all
of that aside for a while.

Now, I'm trying to get back to it and I'm having some problems. A couple of
months ago, I upgraded to Eclipse 3.1.1 and ugraded my plugins too,
including the J2ME stuff. (Actually, I did a fresh install of Eclipse in a
separate directory from my 3.0.1 stuff and then grabbed the newest versions
of various plugins, including eclipseme.) However, I've obviously missed a
step or done something incorrectly because all of my Midlets have red error
flags on them and refuse to run.

Here are the symptoms.

1. Every midlet project has a red flag on it; when I right-click on
properties, and select J2ME from the tree, the J2ME Platform Definition says
"Unspecified Platform". After that, no matter what I click in the tree, I
get a dialog that says "Could Not Accept Changes. The currently displayed
page contains invalid values."

2. _Some_ of the classes in _some_ of the midlets, have this compile error
on the "package common.j2me;" statement: "The type java.lang.Object cannot
be resolved. It is indirectly referenced from required .class files."

I have a strong feeling that the cure is something fairly obvious but it's
been so long that I've thought about midlets that I can't think of what the
problem might be.