Just tried it myself in vain and got the same result as before: MyCloud simply became non-responsive, no access to Dashboard etc. Downgrading to V3 again as we speak - like I did back in May - as it proved to be most suitable approach and stable build (and my Cloud was working like a treat since then).
http://community.wd.com/t5/My-Cloud/Poll-Who-has-reverted-to-V3-firmware-and-why/m-p/874980#M34452
