Just done a fresh install again - twice.
The site is on the same domain. I have used a different cookie & table prefix as I've has issues like this before if I have different forums open ast same time logging into one logs me out of the others.
Anyway - fault in detail:
Doesn't recognise my password. On IE I can request a new password which then works but I can then choose another password. If I set one & then submit I get this message:
There was a problem loading this page:
Invalid Link: Either your permission set does not allow you to be here, or It is possible the forum or topic you are trying to view no longer exists in the database.
Use your browsers Back Button to return to the previous page.
In FF & Chrome I get the same problem plus it won't accept the temp password either.
{edit} correction - FF/Chrome do accept temp password - same as IE