Which version of jboss tools are you using?
Jboss Tools 3.0CR1 compatible with eclipse 3.4.1.
I guess i'm using the nightly builds one? whatever's on the dev site..
I also use Fedora 10.
Using Eclipse Ganymede JEE Bundle (SR1) , and adding the JBoss Tools 3.0.0.CR2 Nightly Update Site  as documented here , I was able to successfully install everything on the site, dependencies and all.
Here's how I start Eclipse:
./eclipse/eclipse -clean -showLocation -data $workspace -consolelog -console -vmargs -Xms128M -Xmx256M -XX:PermSize=128M -XX:MaxPermSize=256M 2>&1 | tee "eclipse.log.`date`.txt"
You could also install the Fedora Eclipse package using yum or PackageKit, then install JBoss Tools into that (make sure the Ganymede and BIRT update sites are enabled). See  above.
Here's the default Java that Eclipse uses (when not explicitly set with the "-vm /path/to/bin/java":
$ java -version
java version "1.6.0_0"
IcedTea6 1.4 (fedora-7.b12.fc10-i386) Runtime Environment (build 1.6.0_0-b12)
OpenJDK Server VM (build 10.0-b19, mixed mode)