This is a third-party bug report. It appears that on RHEL 5.5 a pthread mutex in shared memory cannot be used by a combination of 32-bit and 64-bit apps. I realize that posix doesn't guarantee that this will work since they are technically different programming models, but it seems like a useful capability to have.
*** Bug 11652 has been marked as a duplicate of this bug. ***
This is no bug and there is no way to accommodate such uses because of binary compatiblity with data structures introduced in LinuxThreads a long, long time ago.