Are you running any other programs, or otherwise using significant CPU resources for other applications, while attempting to play Brink? (e.g. Ventrilo, Teamspeak, Spotify, Grooveshark, Media Player)
Since your CPU is at the minimum specifications, you should disable all other major applications while running Brink.
I have no programms in windows tray, except Steam and CCC(Catalyst Control Center). And i have the same freezes on any video/audio(minimumu/maximum) settings. It is not the hardware freezes, that game code problem, fifty-polygonal levels of the Brink can’t take so much resources.
Game have the debug-mode with the conclusion?
Did you try all of these?
http://www.splashdamage.com/forums/showthread.php?t=28694
Especially:
“Disable Catalyst A.I. in AMD Catalyst Control Center”
Disable Catalyst A.I. in AMD Catalyst Control Center
Crispy you my hero!
You need release patch with fix that problem, not all ATI users using official forums for problem solving and they think what game just have bad optimization.