This has been occurring as AMD hasn't been quick to the game with supporting new kernel and X.Org Server releases, until Ubuntu gets around to shipping these updated components of the Linux stack. Fedora, for example, has been shipping with X.Org Server 1.7 for months, but now that Ubuntu 10.04 is getting ready for release, the support is finally about to arrive within AMD's principal graphics driver. For the record, X Server 1.7 was released in October of last year, but it was in development long before that and originally was going to make it out in April.
No Catalyst 10.3 package that bears X.Org Server 1.7 support has yet to hit AMD's web-site, but over on Launchpad is this updated package that was just pulled.
fglrx-installer (2:8.721-0ubuntu1) lucid; urgency=low
* New upstream release:
- Restore compatibility with kernel 2.6.32 and xserver 1.7 (LP: #494699).
- Add Passive Stereo support on workstation (FireGL/FirePro) hardware.
- Add Eyefinity support (more than 2 monitors on Radeon HD 5xxx hardware).
Officially WS-only but should work on consumer boards as well.
* Port packaging to the new alternatives system (LP: #258038).
This updated Catalyst Linux driver has support for X.Org Server 1.7 and the Linux 2.6.32 kernel (though that should have been in the public driver for a month or two now, but there's still no support for the latest Linux 2.6.33 kernel) and it also brings new features. These new features are Passive Stereo support for FireGL / FirePro workstation graphics cards and Eyefinity support (more than two monitors with the Radeon HD 5000 "Evergreen" series). Eyefinity on Linux is what powered the 24 display demo shown last year, which is now officially supported in a public Linux driver.
Users of other Linux distributions depending upon X Server 1.7 will either need to extract the Ubuntu Debian package from the Lucid repository or wait for AMD to officially release Catalyst 10.4 for Linux in April.
Also pulled into the Ubuntu Lucid repository today was the NVIDIA 195.36.15 pre-release driver.