/wp-admin URL redirects to homepage

Hi Guys,

This has been going on a while and driving me nuts!

When I try and go to /wp-admin to log in/access the dashboard – I am immediately redirected to the homepage – which then keeps loading/refreshing every couple of seconds.

Makes using the site as admin/getting to the dashboard near on impossible!

Have tried reinstalling WordPress and also checked .htaccess to make sure I am using only the basic/usual settings.

I have w3 total cache installed, and a Facebook plugin which adds a Facebook login option (mmmm).

I guess the immediate/obvious answer is to uninstall the plugins etc – but it is quite a popular site with a lot of users, I don’t want to break the site if I can avoid it ?? so was hoping someone might know an obvious cause of this I can try.