p.s.- this is pretty well marked:
"Pro Tools LE 7 for Intel-based Macs Pro Tools LE 7.4 (003 Factory, 003 Rack, Mbox 2 Pro, Mbox 2, Mbox 2 Mini, Mbox 2 Micro, Mbox, Digi 002, Digi 002 Rack) are officially supported on Mac OS X 10.4.9 for Intel-based Macs Pro Tools LE 7.3 &7.3.1 (003 Factory, 003 Rack, Mbox 2 Pro, Mbox 2, Mbox 2 Mini, Mbox 2 Micro, Mbox, Digi 002, Digi 002 Rack) are officially supported on Mac OS X 10.4.8 and 10.4.9 for Intel-based Macs Pro Tools LE 7.1.1 (Digi 002, Digi 002 Rack, Mbox 2, Mbox 2 Mini, Mbox) and Pro Tools LE 7.1.3 (Mbox 2 Pro) are officially supported on Mac OS X 10.4.6, 10.4.7, and 10.4.8 for Intel-based Macs
Pro Tools LE 7.1.1 and 7.1.3 will not install or run on PowerPC-based Macs, and Pro Tools LE 7.1 and earlier will not run on Intel-based Macs"
found on the OSX Requirements page... scroll down to Pro Tools LE 7 for Intel-based Macs
http://www.digidesign.com/index.cfm?...4&itemid=22904
Also a main reason why you were able to run PT 6 for so long is because Apple was a lot slower at releasing OS updates which made Pro Tools a lot more stable. And if you choose to keep your operating system version the same for the next two years and also your PT version, you could run on a single version of the software for as long as you want. If Digi doesn't update their versions and make things better, than what's the point? Do you have your auto software updater on? or did the Mac you bought come with 10.4.11 pre loaded.