I've been struggling with this for hours and it's incredibly frustrating.
I've viewed every post I can find that mentions this problem but I still
can't find a solution.

I'm trying to upgrade from 1.38a to 1.5, the DB Upgrade page
has 2 boxes ticked for upgrading from 1.38 to 1.39 and 1.39 to 1.5.

I'm starting to think I should do these separately, but this doesn't seem
possible via the upgrade page, because I've exhausted every other avenue.

I get the following message on trying to upgrade -

Admin Password required to proceed with upgrade

I'm using the correct Admin details, not the configure/DB access details.
I have a duplicate copy of the live site DB that I'm attempting to upgrade.
The duplicate was only made yesterday and the admin details are exactly the same.
I've logged in to the Admin on the live site a number of times whilst trying
to resolve this to check. All the paths in the configure file are correct.

I've even compared the hash password in both DB's via phpMyAdmin
and tried changing the configure file to upgrade the live DB rather than the new
DB. I figured since they match I could just switch the new DB to be live
instead until I was ready. No joy! Still the same error even though I
logged in to the Admin a few minutes before switching the DB
connections around.

I've noticed it's recommended that on accessing the 1.5 Admin you
should not do it with other browser tabs open, I tried that, just the
upgrade page open, nope no joy there either.

I usually cut & paste a password to avoid typos but I tried typing this
in case there was some paste blocking code. Nope.

Nothing has worked I still get the same fecking error!

So what else could possibly be going on? And what's left to try?!

tia,