Issues with the 2.6b1 release of NAMD.

Please see the release notes at http://www.ks.uiuc.edu/Research/namd/2.6b1/notes.html

New Mac OS X binaries are up to 70% faster, but users must download the IBM XL runtime library from http://ftp.software.ibm.com/aix/products/ccpp/vacpp-rte-macos/

There are issues with the Charm++ timer on dual-core Opteron and Athlon 64 clusters that can cause the load balancer to hang. See NamdOnAMD64 for details.