Thanks Siddhartha,
It appears the problem is caused if you have a username that contains an underscore "_" character.
This is a problem with the wiki software and we'll try to find a workaround.
For now, if you find that you can not login and you have an underscore in your username, please leave a message here or contact me directly and I can change your username to one without an underscore.
Apologies for any inconvenience caused.
Please note that you can always edit the Wiki anonymously too!
Best regards,
Kian