I installed FC5 on my machine.
First I backed up $HOME, then I did a clean install.
Then I copied $HOME back. Then I ran Eclipse.
Eclipse forgot about my local update site in ~/.eclipse/.
So, it couldn't find the pllugins I had installed.
However, the behavior was a bit odd... I went to the
eclipse.org update site, but Eclipse didn't offer me any
updates -- as if it still partially knew about some of
my local installs (like GEF).
I manually added ~/.eclipse/.../whatever as a local site
and restarted, and then all was fine. However it would be
preferable not to have to go through this with updates.
This bug is too old to track down. Sorry for not looking into it.