Site vanished

Forgive what is probably kind of an unhelpful title, but I’m kind of new to this side of things. I have had a problem with my feeds updating my facebook notes (it stopped doing it a couple of months ago). I thought that perhaps it was a glitch with a plugin so disabled them all to see if it helped (it didn’t). When I tried to reactivate them all the whole site has collapsed.

No matter what address I enter, whether it’s in the admin, dashboard or the site itself I get presented with the following message:

Fatal error: Cannot redeclare get_sub_cat() (previously declared in /home/leadin17/public_html/wp-content/plugins/collapsing-categories/collapscatlist.php:195) in /home/leadin17/public_html/wp-content/plugins/superslider-menu/superslider-menu-list.php on line 140

So it seems that the collapsing categories plugin has done something or other, but how do I go about fixing it if I can’t access the dashboard? Is it a matter of installing a backup? (Thankfully I took a new backup before starting to tinker). If so, how exactly do I go about that without the dashboard!? I know this is probably fairly elemental stuff but I’m lost.

Once I get the site back up I’ll start another thread about the Facebook issue!

Thanks folks.

Dougie

PS – the site is: leadinglinesphotography.net