I can't think off the top of my head a reason why that'd be the case. I've not been able to replicate, so it's not something systemic.
You self hosted or hosted? Any warnings or errors on your diagnostics panel? Are you doing something like editing on HTTP but posting to HTTPS or the other way round? (in which case the POST could be being rejected)
All else fails you could capture your save exchange in your browser's dev tools and email me the exchange (marcus at dushka.co.uk)