This issue is resolved. All VMware Communities participants should be able to update documents and save their changes without errors.
As mentioned before, the problem was caused by our use of Akamai Dynamic Site Accelerator (DSA), which we resolved yesterday. Akamai DSA improves network performance by re-routing traffic via faster network connections, but in our initial configuration, this caused jsessionids to change. The VMware Communities platform requires these to stay the same across the session so that requests from an individual user route to the same server in our back-end application cluster. We've now changed the configuration to preserve jsessionids, which solves the problem and allows us to continue to get the performance improvement from Akamai DSA.
Thanks all for your patience as we worked through this issue.
Regards, Robert
Robert Dell'Immagine, Director of VMware Communities