Server Error in '/PMUser' Application. Resource already exists'


Was altering the user.xml file to update some text on our front page, but after restarting service and resetting iis, I get this error on the screen

Server Error in '/PMUser' Application.  Resource 'xxxx' already exists'

And even when replacing the user.xml with the original (that I copied before altering) it still gives me this error.

I even tried to reboot it.

Where can I start trouble shooting?