The Air Users Blog which you should follow if you're a Protools user posted that Avid has released the PT 9.0.5 update for MacOS X Lion.
From Avid's page:
Although not officially qualified, Pro Tools 9.0.5 also adds public beta support for Apple's OS X Lion operating system.
Known Issues in Pro Tools 9.0.5 (Beta) on Mac OS X 10.7.x ("Lion")
Pro Tools 9.0.5 adds public beta support for Apple's OS X Lion operating system. Please see the Pro Tools 9.0.5 Mac Read Me before you update for important information on installing the Lion operating system and installation and use of Pro Tools 9.0.5, including the following:
Upgrading to Lion can result in the uninstallation of Pro Tools components.
If you upgrade from Mac OS X 10.6.x ("Snow Leopard") to Mac OS X 10.7.x ("Lion") with Pro Tools already installed, DigiDioMIDIServer.plugin and DigidesignFireWireMIDI.plugin will be uninstalled during the Lion install.
If you subsequently try to launch Pro Tools, a dialog will appear indicating that these files were moved to an Incompatible Software folder.
To run Pro Tools on Mac OS X 10.7.x ("Lion"), create a clean Lion partition and install Pro Tools directly to that partition. Avid recommends against updating a Snow Leopard partition that already had Pro Tools installed due to the potential for Lion to uninstall certain components during its installation process.
The Send To DigiDelivery command in Pro Tools will not work with Mac OS X 10.7.x (“Lion”).
The DigiDelivery client application requires Rosetta to be installed. Mac OS X 10.7.x does not support Rosetta. The Send to DigiDelivery command in Pro Tools will not function on Lion.
Please see the Pro Tools 9.05 Read Me for additional known issues.
Pro Tools 9.0.5 Read MeThese Read Me files document important compatibility information, issues resolved in Pro Tools 9.0.5 (including issues resolved in 9.0.4 Mac, 9.0.3, 9.0.2 and 9.0.1), known issues, error messages, and information on installation and use of Pro Tools 9.0.5 and Pro Tools HD 9.0.5 software:
Get more info on the PT 9.0.5 update here.