I've been using Adium for some time now.
I recently added a AIM account with my email address, but now my username is too long for Adium so I can't go online with it.
I would post this as a bug, but I don't know where the bug tracker is
I'm using Adium Beta 15.
Is there a file I can edit to extend the available characters by 1?
the bug tracker is at trac.adiumx.com, however I think you are doing something incorrectly. AIM accounts are not email addresses and have maximum lengths. If it is an AOL address you can drop the AOL.com, if it is a .mac address choose the .mac option and it will add the .mac for you.
Or go to http://aim.com and click on Get screen name... they have 2 options... the first one you get an AIM screen-name, the second one is an option to use your existing email address.
I used an address, which I am able to login to aim.com with it, but it's 1 character to long.