Eclipse 3.4 is not in the Ubuntu repositories of Ubuntu 9.10 Karmic Koala. So if you need it for any reason, you need to download the tarball from eclipse.org and install it yourself. If you follow the normal procedures for that, you might receive the following error message in {$ECLIPSE_WORKSPACE}/.metadata/.log

!ENTRY org.eclipse.osgi 4 0 2010-01-26 18:28:31.518
!MESSAGE Application error
!STACK 1
org.eclipse.swt.SWTError: XPCOM error -2147467262
        at org.eclipse.swt.browser.Mozilla.error(Mozilla.java:1638)
        at org.eclipse.swt.browser.Mozilla.setText(Mozilla.java:1861)
        at org.eclipse.swt.browser.Browser.setText(Browser.java:737)

Above that last error, there can be many “java.lang.RuntimeException: Widget disposed too early!” messages.

The solution I found was in the Ubuntu Bug #237081 log where somebody tried to install Eclipse 3.4 RC1 and RC2 on Ubuntu 8.04 Hardy Heron back in 2008, for 32 bit Linux. It works also for me (64 bit Ubuntu 9.04), so the problem and solution seem to be both quite general.

Now, the steps how to do the installation:

1. Download Eclipse Classic 3.4.2 (eclipse-SDK-3.4.2-linux-gtk-x86_64.tar.gz) from here.
2. Unpack the tarball into /usr/local/share/applications/.
3. Rename the resulting eclipse/ directory to eclipse-3.4.2-64bit/ if you like (for example, to separate it from other Eclipse installations in that directory).
4. Install the Ubuntu package named xulrunner. It does not help here if you have the xulrunner-1.9.1 package installed, as Eclipse seemingly cannot find this one. The version that I installed was 1.8.1.16+nobinonly-0ubuntu1.
5. Add the following line to the eclipse.ini file of the Eclipse 3.4.2 installation, at a place somewhere below the -vmargs line:
   -Dorg.eclipse.swt.browser.XULRunnerPath=/usr/lib/xulrunner/xulrunner
6. Start Eclipse (maybe you need the -clean option).
7. Now you can remove the line from eclipse.ini again (I do not know exactly why this is the case; it seems that Eclipse now is able to find XULRunnner 1.9.x, which it could not before because the path was different from its expectations).

However, the sad news is that this does not cure all problems in Eclipse. Eclipse might show many NullPointerExceptions, some XPCOM errors, and the like. Additionally there is a bug related to GTK 2.18 (making it impossible to press buttons normally) which is cured only in Eclipse 3.5.2 (and in some Linux distros before that release). There is this alternative howto that you might try out (I did not).

But in all, it seems you are better off by going with Eclipse 3.5.x and solving the problems you encounter there.