After changing the style from oxygen-gtk to QtCurve, my Eclipse is now running on steroids.
I'm using Eclipse Indigo 3.7.1 on Kubuntu 11.10 amd64 with Oracle JDK 1.6.0_26 and an NVIDIA GeForce 8400 GS graphics adapter. I never used to have any issues on Kubuntu 10.04 LTS which is still running smoothly on another partition of my disk.
I had suspected the NVIDIA drivers, tried different JREs (including 32 bit versions) and Eclipse releases, none of which made a difference.
Finally, changing various configuration options by trial and error, I found out that
oxygen-gtkseemed to be the cause.
To optimize your installation, install the
qtcurvepackage, and select it in K Menu | System Settings | Appearance | GTK+ Appearance | Widget Style. Then restart Eclipse and enjoy.