Problem adding and deleting posts

I am having a problem with my wordpress.

Whenever I add or delete a post it goes to a blank page (although the post is updated).

Also whenever I try to delete a post it also goes to a blank page but the post doesn’t get deleted either.

I’ve tried re-uploading the wp-admin directory but that doesn’t fix it.
Can anybody else think what might cause this?

(I should also mention, it used to work but I have been moved across to a new server by my host)