I have the same problem but found something strange.
Don't know if this could help
I've tried my 64 alpha-num chars password and it fails many times.
I've change my wireless router password to an 8 alpha-num chars password and it then work when I tried to connect the PI to the network...
Of course I could not keep this password and had to put back my 64 chars pass, but the problem came back, i can't connect to network, displaying again the same invalid argument message.