Problem downloading game from Oberon Media

I recently purchased on online game from Oberon Media through Comcast. The demo downloaded just fine, but once I purchased the entire game, I repeatedly got the dreaded "crash" alert. I sent a report to Apple, and also to Oberon Media. The Apple screen said the download "must be run on an account with Computer Administrator access." This is puzzling because my computer is not networked, and I am the "administrator," but my password (which works on everything else) isn't recognized. When I contacted Comcast, they said they had no control over any of this. Oberon Media says it's an Apple problem. Apple hasn't responded at all. Needless to say, I am very frustrated, because I'm now starting to have more problems with my eMac than with my husband's PC! Any ideas from those of you who have purchased and downloaded (or tried to) an online game from anyone other than Apple??