[Q] CM11 upgrade (2014-08-01 to 2014-12-10) via CWM softbricked i8150 topic

Hey,
Had tried to upgrade from CM11 2014-08-01 to CM11 2014-12-10 (the version not (!) having the changed partition layout).
Configuration before upgrad was:
CM11 2014-08-01, CWM v6.x
What I did:
-) Used ROM Manager to do Backup of existing ROM -> failed (not enough memory on SD card/internal), tried again after changing ROM Manager settings to write backups onto external SD -> failed again (i.e. didn't even start; extenal SD has ~5GB free, so no space issue there).
-) Then I noticed that suddenly ROM Manager said it was running on v5.x (but I had v6.x installed). Did upgrade to v6.0.5.1. Worked.
-) Then used CWM to boot into recovery and install CM11 build 2014-12-10 (file: cm-11-20141210-UNOFFICIAL-ancora.zip in external SD and MD5 checked to be OK). Then in CWM did the following:
-) install zip from external SD -> started OK but stopped once installing from zip (progress bar did not start to show anything and did not appear even after 30min). Phone did no longer boot (Samsung logo apears then Sampsung Galaxy logo but w/o CyanogenMod logo then black screen...)
-) took battery out, back in and into CWM recovery (still v6.0.5.1)
-) wipe data
-) wipe cache
-) wipe dalvik cache (in advanced)
-) format system
-) format cache
-) mount USB and download the and then downloaded cm-11-20141210-UNOFFICIAL-ancora.zip again onto external SD
-) interestingly, only the external but not (!) the internal/SDcard is visible in Windows explorer ?!?
-) tried again to instal from external SD -> failed again with same issue as stated above.

Please help me getting my Galaxy W back to working order!
Many thanks in advance,
Frugi