I've seen a somewhat similar thread about updating GC but that seems to have worked fine. However, when trying to update the media I get the following dumped out by the log file. I would guess that gc2_multimedia.sdc isn't valid as it's only 57 bytes but any suggestions are welcome.
I also tried uninstalling the multimedia pack and then installing again but that didn't work. Neither did a SDC reinstall.
-- [Installation] ---------------------------------------------------
Download: C:\Program Files\Stardock\SDCentral\data\public\gc2\production\gc2_Multimedia.xml 1
Load: C:\Program Files\Stardock\SDCentral\data\public\gc2\production\gc2_Multimedia.xml 1
Download: C:\Program Files\Stardock\SDCentral\temp\gc2_Multimedia.sdc 1
Extract C:\Program Files\Stardock\SDCentral\temp\gc2_Multimedia.sdc 0 (sdczip error code 1)
Result: Installation failed (21)