when that error occurs, did you see any suspicious entries in your error log?

I already have a functioning elgg installed at a different domain. Same web host. No problems.

are you on a shared hosting plan?

I don't have direct access to my hosts error log.

Yes I am using a shared hosting plan

when you fresh install again, did you make sure to erase the old database and make a new one or at least dump the tables

I dropped the database entries yes, the installation told me to. Next time I tried again, I dropped them beforehand.

Are you using any special characters and/or spaces in the admin username? This could result in the error as no such characters are allowed within the username. Unfortunately, there's currently no error message telling you this - will be fixed in the next release of Elgg though.

Try repeating the installation with using only "normal" characters in the Elgg admin username.

Should I tro to completely erase the database and make a new one?

make sure admin usernames are more than 3 characters