Same as I've said before. Many times over for the 'undefined' issue.
If you come across this issue be it when you PM or post, it is a browser problem! Just clear your cache/history/cookies, go through your add-ons (these are probably the culprit, it's a matter of figuring out which one(s)), and the getting rid of the problematic add-ons. Once the add-on(s) are gone, restart your comp and try logging in again.
Again, this is a BROWSER problem. WE KNOW OF IT. There are a slew of threads in Q&S about it, some even having the title indicating as much.
Anyway, hope this helps. Good luck.