The Margaritaville Nashville location now has a Facebook page.
http://www.facebook.com/MargaritavilleNashville
Their page says the opening is this fall but newspaper reports are saying the opening is December. Delays with design proposals may mean an even later opening date. 
The building re-design Margaritaville presented to get a construction permit was rejected because it does not comply with codes requiring buildings in downtown Nashville to look ‘historically correct’.
From an article in the Tennessean newspaper:
“The real sticking point is our operable storefront windows that can be opened in good weather, and they’re a key element of the Margaritaville Cafes,” said Mark Bloom, a principal in the Corner Partnership, which owns the three-story building and is paying to develop the beach-themed restaurant.
The Metropolitan Historic Zoning Commission, which governs the look of buildings in the city’s historic district, wants a more traditional storefront with glass that doesn’t flop open. Here is a link to a legal document (PDF file) at the Nashville Metro Historic Zoning Commission describing the situation:
http://www.nashville.gov/mhc/pdfs/agendas/mhzc/2010/100317_322Broadway.pdf
Parrotheads (especially in middle TN) hope they work things out soon.
UPDATE – Here is a picture of the building as it looked noonish Saturday Feb 27 2010.
Each month at our club Happy Hour we collect spare change and aluminum can pull-tabs for the 
