Thread:Project:Support desk/Admin is unable to login - "invalid username"

All of a sudden MediaWiki returns an "invalid username" error message when I login to my wiki at www.chronistwiki.de (or "illegal username", the Wiki is German so I don't know what the exact English version is). All other users can sign in without problems. After the problem first appeared, I did some hacks to the database in order to change (or rather, cripple) my username (from Nuhrii the Metruan to Nuhrii the M) and I was able to login without further problems. I even tried to create a new account and assign my old username to it, but MediaWiki denied it as invalid. Afterwards, I restored the initial database because which I had backed up before I made any hacks. Do you have any advice how I could solve this problem and findally be able to login again? It would be very appreciated.

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