I've had the same issue, left with no option but to reinstall. I know they do their best and I'm very grateful for the game, it's brilliant but this is definitely a recurring issue. I'm blessed with having a very fast internet connection and an SSD so it's not as painful as it used to be but forget to back up your customised settings and you're in for a long day!

Just an update from me in case it helps anyone else. I had the same issues and I managed to login successfully AFTER the recent patch. To rectify I've uninstalled the game and after pulling a new installer I noticed(Even though it was freshly installed on a new computer last week) the new installer defaults to the x86 directory even though the game is 64bit now. Yes I have a 64 bit computer before anyone questions that.. so I changed the default directory, recreated the folder structure in Program Files, done a fresh install just now and it seems to have got me round the issue. I did take a backup of my settings too from App Data > Local > SWTOR just in case and repopulated them back in after launching the game once. Very strange considering I was logged in Friday evening and I had no issues. This has got me round the issue though for tonight anyways. Hope it helps!