Blinkthinks, who first noticed that Navifirm is now locked down, reports that there is a work-around, at least for current ROMs, for downloading from the server.

They write:

DO NOT CLEAR THAT NAVIFIRM CACHE!!! If you guys still haven’t cleared your Navifirm+ cache, D-O-N-T. Make sure you save that cache using WINZIP, or WINRAR or any compression utility. Then upload it somewhere and post a reply in this thread. Apparently if you still have the cache INTACT, you can still download from Navifirm. The cache folder can be found inside the Navifirm+ 1.7 folder.

Presumably this will not allow future ROMs to be downloaded, but may be useful for those who are suffering a bricked device.

Read more at Blinkthinks here.