Critical "Encountered an improper argument." dreamseeker freeze/crash/disconnect on login

[bf_taka]

Whenever I try to connect to a Goonstation server I get a dreamseeker popup that says "Encountered an improper argument." along with a Windows error sound the moment I connect and the Character Setup window appears. The Dreamseeker client then becomes unresponsive (clicking anything in Character Setup doesn't do anything) and about 30 seconds later I get a red "You are either experiencing lag or the connection has closed." message in the chatlog.

This happens to me every time I try to connect to Goonstation #2, and makes it completely impossible for me to play.

Things I have tried:
-Upgrading to the latest (512.1423) version of BYOND
-Also trying versions 512.1421, 512.1422, 512.1401
-Completely uninstalling and reinstalling BYOND
-Connecting to Goonstation #1 (same error)
-Creating a new BYOND account and connecting with that (same error)

I think when I tried to connect for the very first time I may have gotten a message about my character data being out of date/in the wrong format and being reset or something like that. That message doesn't appear anymore so I don't remember exactly what it says. My BYOND account is Takanago and I used to play as Burt Norman.

I would appreciate any help you could give me with this, even just a workaround because I just can't play at all with this. I've managed to play on Goonstation from this computer before but I can't now.

[bf_taka]

Any way I could get some help with this? I don't want to nag but this is completely preventing me from playing on Goonstation. I tried deleting my Documents/BYOND/ folder (which made BYOND forget my account data, made me re-download resources, etc.) and try logging in after that but I still got this error. I also tried logging in with a different account again and still got this error.

[Gannets]

I can't say I've ever ran in to this issue before, so I don't have a great deal of advice.

General troubleshooting tips are to update to the latest byond 512 beta, clear your cache and make sure IE is up to date too.

[mbc]

Update IE, update directX, update your graphics drivers, turn on ActiveX filtering in internet explorer, and make sure your antivirus isn't messing with things.
Also if you're using a laptop with a dual integrated / GPU setup, make sure to flag dreamseeker.exe as an application that uses your GPU and not integrated card.