Issue with login to admin on magneto site

Hello

We have a site that uses magneto. The site works fine but when we got to admin we get a 401 error.

We have had the data centre look at this and its nothing to do with the hosting. It use tow working fine until the data centre did a server migration messed up the innodb and then since the restore the admin page just goes to a dead 401 page instead of a page that lets us log in.

I have had a few coders look at this and they couldn't fix it and told me I need some one that specialises in magneto.

So if you don't specialise in magneto please don't contact me I will only be speaking with people that can fix this error.

Thanks