Plugin 404 Error

Hello All,
I have a worpress site: http://www.sheedadesigns.com, my web host is Arvixe. I have 10 updates and 4 plug in updates that I need to do. However, I cannot update anything without receiving a “404 Unfortunately, the page you tried accessing could not be retrieved.” error. I also cannot go into the general tab. I need to add new plug ins to my site and do the updates and maintenance to my site but I cannot edit anything! please help.