I would recomment to use the bitshare_client.exe which is a terminal version without GUI .. to let the blockchain sync initially
When using a chainserver you should see some lines stating sth like "fast download" IIRC .. there should not be a mention of P2P when downloading from chainserver ..

after syncing you can close the teminal version via 'quit' and run the GUI version as usual

I'd like to add something to this that may in fact help out quite a few users. I've been struggling myself to get the blockchain downloaded after upgrades and reinstalls, and I think I've found a reliable way to engage the chain servers.

Initially removing the "default_peers" portion of the config caused the chain server to engage successfully for a little while (as demonstrated in the "info" command output. However, after a brief period of d/l'ing from the chainserver (in this case, liondani's), the client seemed to discover the default peers, and flip over to a slow p2p sync. It also re-added the mising peers list to the config.json. So no joy there.

However, after changing "maximum_number_of_connections": 0 in config.json, it appears to be sticking to downloading from the chainserver and not establishing p2p d/l connections. It's been stable for about ten minutes for me so far, and has downloaded up to 510856.

Hope that helps some of you.