Issue creating sub-domains in WordPress Multi-site

I'm in the process of setting up an Etsy like store front with Marketpress, MP front end, and WordPress multi-site. I've got it mostly set up ... but it doesn't seem to be working properly.

I'm able to register the new sub-domains ... and when clicked on, they go to a blank screen (which I'm told is what is supposed to happen) ... but then when I try logging into them at /wp-admin I get the following error:
[an error occurred while processing this directive]

My main URL is

None of the sub-domains are working. Here's an example of one for reference if needed:

I REALLY appreciate any help!!!!