Blank Page when removing Multisite

Hey,

I'm trying to remove Multisite (www.israsport.co.il) but i come across so many problems.

The main problem is when i delete or change define('MULTISITE', true); to false, i get a blank page. doesn't matter if i delete all the multisite lines, or just this one, i get a blank page time and time again.

I deleted all caching plugins and files. that didn't help.

Any ideas?

Thanks