That makes me wonder, can CS4 still open .PSDs of older Adobe versions?
Maybe try making your own brushes if you can?
Its quite typical for a new Adobe Collection to take a long time to arrive on the first year of its release, with many others wanting to get their hands on the program.
But you can open older files in the new version. The school has CS3 and I can open it at home on CS4. CS4 has a new feature... so you probably can't open it the other way around. Which applies to most programs.