The problem (from my perspective) was caused by the Reboot and Rescan that MyCloud had to do after the Firmware 4 update. This made the boxes temporarily useless which confused many of us for quite a while.
Below is what I think is the technical explanation (and solution) for us users of MyCloud.
It looks like MyCloud now really hates multi-tasking and that, after you add new files to MyCloud, it has to Rescan the database - which renders the device totally useless until the Sanning is completed.
So if you leave your MyCloud alone after the update to firmware 4, for a while, it will all fix itself and you will be back in business - until the next time it has to rescan it’s database (i.e. until you add/remove files to your device)
The SOLUTION (if WD can’t fix this through another update):
Is to turn off automatic Rescan of the database (because the drive is useless while it is scanning your database), and to do it manually after you change your database and when you are not going to need the drive for any other purpose for a while (i.e. until the Rescan is completed). Then you can continue to use it at it’s maximum (best) performance potential.
THE PROCEDURE:
open the twonkey interface on port 9000 i.e. wdmycloud.local:9000
go to Advanced menu and click Clear Cache then
set Rescan Interval to 0 instead of -1 (This will effectively stop the software (Twonky) from rescanning your files.
then go to Dashboard (your admin web interace) and turn off Media DLNA server in:
Settings, Media, Media Streaming, OFF
then select Rebuild database (if you suspect database corruption)
or
select Rescan (To Search for changes to your files)
and wait for it to finish.
After that, reset Media Streaming to ON (so you can start streaming to your devices again)
and then either go back to Twonkey, Advanced settings and change the Rescan Interval back to -1 (to re-enable automatic file scanning)
OR
Leave it at 0 in Twonky (which is what I am doing) and use the Rescan option in Dashboard after you are done modifying your files. i.e. Dashboard, Settings, Media, DLNA Database, Rescan
BUT remember that your device will still be useless until the Rescan completes in Dashboard (also you won’t need to turn media streaming off and on again if you are not using the box until the Rescan completes).
THANKS to nabulaer (above) for posting his solution to this problem, which helped me in resolving my problems and to try to explain it further and to help somebody else.
I have also passed this info to WD when they contacted me on the trouble call. It’s still a good device and keep enjoying this cool device.