Update: it seems like a lot of people find this useful. With the final release of Ubuntu 10.04 Lucid Lynx, xulrunner-1.9.2 is in the main repository. Because of this, just uninstall xulrunner-1.9.1 and you’re done.
I like living on the edge: I use Ubuntu Lucid and Eclipse 3.6M5 on my x86-64 notebook. Since the 25th of February, Eclipse started crashing when closing the content assist popup window. I narrowed it down to the upgrade to libcairo2-1.8.10-2ubuntu1. This causes a RenderBadPicture X Error when the documentation popup that appears on the right of the possible completions is closed. Downgrading to libcairo2-1.8.8 solved the problem, but it seems that the real problem lies within xulrunner 1.9.1 which SWT uses to render the docs. The Mozilla bug is https://bugzilla.mozilla.org/show_bug.cgi?id=522635. A quick workaround is to set the GRE_HOME environment variable to some meaningless path (e.g. /tmp) before launching Eclipse. Another possible solution is to install xulrunner-1.9.2 (only available from the mozilla-daily-ppa). I have filed a bug report un Launchpad asking for an official upgrade to xulrunner 1.9.2.