When broadcasting,website goes down

Hi,

when im publishing a new post immediately or scheduled and i also want to get them broadcasted ,at the same time from my computer or another computer/network,my website shows an internal error. After a while everything is getting better till the next publish.
I have 2 twitter and 6 facebook accounts.

http://ww.wp.xz.cn/plugins/social/

My website is http://www.beefree.gr