Error 500 on post.php after moving to another host

I’ve just move from a host to my personal VPS running Kloxo control panel. I was able to transfer all my files from the old host (moved everything using FTP) including the database.

I modified the wp-config.php file with the new database name and password (the older database was backed up and then imported to the new database, thus making both of them the same).

I’m able to view the site and modify the site, but every now and then I get some 500 errors which are fixed by just reloading (that´s something extra if oyu can help) but my main issue is with posting.

I can do a new post, but while posting it gives me the 500 error. The thing there is that I can go back to the site, and the post will actually show up. NOW here’s the bigger problem. I can’t try to edit the existing post because it will give me an error 500 again, this time without a reload fix.

Advice? Thanks!