Unable to install Xcom after download from MAS

Since yesterday i try to install the game Xcom: Enemy unknown - Elite Edition from the Mac App Store (MAS).

The game downloads fine - wich takes close to 2h for the 13,5gb - and then the button switches to "installing" wich suddenly ends with "unknown error", please try again. and boy i've tried..

now it's the second day downloading this over and over again and i'm seriously pi**ed that i didn't use ferals online store but the MAS.

i hope someone has any hint what i can do?

what i already did:

1) deleted the file and tried again

2) deactivated "little snitch"

3) cleared the cache and tried again

4) cleared the temp cache and tired again

5) used onyx to clear the system, cleaned the app store cache, rebooted and treid again

6) set up a new user and tried again

all in all nothing worked for me. and after 5x times downloading (thats 10hrs!) i'm seeking for wisdom that goes beyond my google skills.

any help appreciated.

thanks,

robotobi