Sun support has not provided any more information about the potential bug.
We just noticed that the x6450 blade modules are no longer sold on Oracle's website, which makes resolving this issue moot for us. Even if the issue was resolved, we'd have 10 blades across two chasses that we couldn't expand. Moving all ten x6450 blades to one chassis and putting other blades with potentially different processors in the other chassis would cause issues with Site Recovery Manager. It makes more sense to replace these blades with ones that work than to keep waiting until a blade locks up, generate diagnostic logs, forward those to support, and get the call that the logs don't include any clues as to the cause of the lock-up.
We've focused on working with our Sun sales rep. to replace the x6450's with their AMD counterpart, the x6440's. From what I can see, the x6440 is the only 4-socket, six-core blade that's both available for sale and supported by VMware. Of course, the x6450 is supported by VMware, too. We'll see how that goes.