Error after clearing cache

[vaios]

Hi gurus,

I have just dublicated Joomla 2.5.9 (Parallels plesk) to httpdocs/site1.
I upgraded it to 3.1.5 and except the strange menus everything went ok.
When i cleared cache everything stopped.
I get an http 500 error on my ie, nothing on firefox or chrome and 301(redirection)
when using httpping utility. I'm stacked. Can u please help as i cannot find any logs.
(/site1/logs).


Thanks in advance.