Portal 2 crash on Mac

Process:         portal2_osx [420]
Path:            /Users/USER/Library/Application Support/Steam/*/portal2_osx
Identifier:      portal2_osx
Version:         ???
Code Type:       X86 (Native)
Parent Process:  steam [380]
User ID:         501

Date/Time:       2012-08-06 23:09:58.016 +0100
OS Version:      Mac OS X 10.8 (12A269)
Report Version:  10

Interval Since Last Report:          57309 sec
Crashes Since Last Report:           14
Per-App Crashes Since Last Report:   7
Anonymous UUID:                      9FC19770-19CB-4F9B-A174-C9B9ABD367F1

Crashed Thread:  20  CIPCServer::Thread_MainLoop()

Exception Type:  EXC_BAD_ACCESS (SIGSEGV)
Exception Codes: KERN_INVALID_ADDRESS at 0x00000000e9609ea1

VM Regions Near 0xe9609ea1:
    CG backing stores      00000000c77c6000-00000000c81c6000 [ 10.0M] rw-/rw- SM=SHM
-->
    Submap                 00000000ffff0000-00000000ffff1000          r--/r-- process-only submap